Caramelized onion relish for hamburgers

Need a secret ingredient to up your burger game this summer? Try caramelized onion relish. This sweet and soft red onion relish works great on any burger. Delicate and sweet, top your burger patty with a layer of onion relish and enjoy the rich flavour that this condiment adds. This sweet onion relish whips up in just a half hour. Just the time it takes for the burgers and halloumi to get nicely grilled.

Caramelized onion relish for burgers. The secret ingredient to up your hamburger game.

For many people onions in burgers are a love-hate matter. They add some wonderful flavour, but often they’re hard on the stomach. A lot depends on the type of onion used, of course. I am quite sensitive to raw onion, but I seem to do pretty well with Tropea onions. In general, soaking the onion slices in ice water helps, but sometimes it just doesn’t happen. Still, I don’t want to skip the onion altogether because I love the flavour – when it’s not overwhelming. Perfectly balancing raw onion in hamburgers is an art.

Two onions on a cutting board, one is cut in half.

I have no problem with cooked onions. They’re way easier on my digestive system and their aftertaste doesn’t linger for hours. Since I like my burgers with onion but with minimal consequences, I started making caramelized onion relish. This is something I came up with a few years ago, when we first moved to Sweden. Fascinated by the long summer evenings, we took the habit of having BBQs. It would not happen often, but it started integrating into our summer routines.

You see, when you move to a different country – or even to a different city within the same country – you need to embrace the new identity you take up. This is inevitable, I guess it’s part of the adaptation process to the new place and routines. You end up crafting a new side of yourself in the new place you call home. Especially since we moved to our second apartment in Sweden we started loving eating outside. This was something that had barely ever happened in Poland as we didn’t even have a balcony there. But here we have a lovely porch, and dining in the cool summer evening is a real bliss.

A jar of caramelized onion relish.A jar of caramelized onion relish.

So on one of our first grilling ventures with friends I decided to whip up some caramelized onions for burgers. Through trial and error this is the recipe I came up with. At first I had used a little too much butter. It was a fantastic condiment, but it made the whole burger feel way too greasy. And the perfect hamburger is juicy but not greasy. After learning to go a bit easier with the butter (a difficult task, as I am a huge butter lover) I found the perfect proportions for my caramelized onion relish recipe.

A jar of caramelized onion relish.A jar of caramelized onion relish.

Caramelized onion relish recipe

To make this onion relish you will need:

  • 2 medium red onions
  • 30 g butter
  • 3 tbsp granulated sugar
  • 3 tbsp Balsamico vinegar
  • pinch of salt
  • 200 ml boiling water

Start by melting the butter over medium heat. I like to use a non-stick frying pan; make sure you have a lid that fits your pan as part of this recipe calls for covered cooking. While the butter melts, slice the 2 onions. Add them to the pan and raise the heat to medium-high. Sautée the onions in the butter for 10 minutes, stirring them constantly. The goal here is to nicely sweat the onions and get them to become soft, but we want to avoid crispiness. So we need to prevent the onions from frying in the butter. In order to do that, you should never let them sit in the sizzling fat and this is why we move them around all the time. In the meantime, set the water to boil, so that it will be hot when it’s time to use it.

After about 10 minutes the onions should have become quite soft. By this time, the natural sugars in the onion and in the butter will have started to caramelize, so now it’s time to add the actual granulated sugar. Stir in the sugar making sure to distribute it all over. Keep stirring on medium-high heat for a couple of minutes, then pour in the Balsamico vinegar. Again, stir for a couple of minutes, until the vinegar evaporates.

Lower the heat to medium, pour in the boiling water, stir to even out the onion slices and cover. Let simmer for about 15 minutes, checking from time to time to make sure nothing sticks to the bottom of the pan. Depending on the size of the onions and the thickness of the slices, a little more water may be needed. After about 15 minutes, the onions will have absorbed most of the water. Remove the lid and simmer for a couple more minutes to evaporate any excess water. Remove from the heat and serve on your favourite burgers.

A jar of caramelized onion relish.

Beef and halloumi burger with caramelized onion relish

One type of burger I love to pair my caramelized onion relish with is a combination of meat and halloumi. I like to use brioche bread and I will shamelessly say I always have it store-bought. One day I’ll make my own. But everything else is made from scratch, so yeah. I should really start making my own hamburger bread.

So what we have here is a meat patty made with 100% ground beef, salt, black pepper, cayenne pepper, meat masala spice mix and a splash of Worchestershire sauce. If I’m not grilling outside I’ll just cook it on a non-stick pan with no fat. On the side I’m grilling my slice of halloumi on a grill pan.

My sauce of choice is home-made mayonnaise mixed with a couple teaspoons of grainy honey mustard. A leaf of lettuce and, of course, my own caramelized onion relish. I recommend to have mayonnaise both on the bottom and on the top; and of course to grill the bread if possible.

Hamburger with caramelized onion relish, grilled halloumi, beef patty, mayonnaise and lettuce. Closeup of a hamburger with caramelized onion relish, grilled halloumi, beef patty, mayonnaise and lettuce.

 

This is just my suggestion for a great burger, but any burger will love this red onion relish. You can try for example these falafel burgers if you want to skip the meat.

Caramelized onion relish for burgers. The secret ingredient to up your hamburger game.

A jar of caramelized onion relish.
5 from 9 votes
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Caramelized onion relish

A perfect condiment to your favourite burger, caramelized onion relish gives this sweet tone and makes your burger onions easier to digest! Perfect with a beef and halloumi burger!

Course Sauce
Cuisine French
Prep Time 5 minutes
Cook Time 30 minutes
Total Time 35 minutes
Servings 4 people
Author Eva

Ingredients

  • 2 medium onions (about 300 g cleaned)
  • 30 g butter
  • 3 tbsp granulated sugar
  • 3 tbsp Balsamico vinegar
  • 200 ml boiling water

Instructions

  1. Clean and slice the onions. Melt the butter on medium-high heat and add the sliced onions. Sautée for about 10 minutes, stirring constantly to prevent the onion from frying; it should just sweat and get soft. Set the water to boil.

  2. After 10 minutes, add the sugar and stir for a couple of minutes. Then pour in the Balsamico and stir until it has evaporated (another couple minutes). Pour in the boiling water, close the lid, lower the heat to medium and let simmer for 15 minutes, checking from time to time.

  3. Remove the lid and simmer uncovered for a couple of minutes to evaporate any excess water that has not been absorbed by the onions. This is ready to serve.

Recipe Notes

Store any leftovers in an airtight container for up to a week. The butter will solidify in the fridge, so I recommend microwaving before the next use to get to the original texture.

 

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28 Comments

  1. giulia August 8, 2016 at 15:28

    Caramelized onions!!!! Li adoro ed era da un sacco che cercavo una ricetta fatta in casa e questa è perfetta e cade proprio a pennello.

    Reply
    1. Eva August 8, 2016 at 20:20

      Ah che bello, mi fa piacere che questo posta cada a fagiolo 😀 Enjoy!

      Reply
  2. Pingback: Falafel burgers with halloumi and guacamole – Electric Blue Food

  3. Pingback: Falafel burgers with halloumi and guacamole - Electric Blue Food

  4. Carrie | Clean Eating Kitchen May 31, 2019 at 16:21

    What a great addition to any burger! It looks so full of flavor and super straight forward to make! Hoorah for grilling season!

    Reply
    1. Eva May 31, 2019 at 21:42

      Yes! Grilling season is one of the highlights of summer!

      Reply
  5. Amanda May 31, 2019 at 16:28

    It looks like my burgers are getting a serious upgrade this summer! This relish adds so much incredible flavor. Looking forward to making this all summer long!

    Reply
    1. Eva May 31, 2019 at 21:42

      I hope you enjoy! You can definitely call it an upgrade 😀

      Reply
  6. Amy May 31, 2019 at 19:25

    This looks so yummy — the perfect way to spice up any summer cookout! 🙂 And I could totally see it going on more than just burgers!

    Reply
    1. Eva May 31, 2019 at 21:43

      Oh yeah you can totally use it one other things, too. Like on a ham sandwich, it pairs great!

      Reply
  7. Mama Maggie's Kitchen May 31, 2019 at 21:56

    This Caramelized onion relish for hamburgers looks SO deliciously good. I wish I could eat that right now!

    Reply
    1. Eva June 1, 2019 at 22:35

      It really does look pretty. Like a proper onion jam. The texture is the best thing about it though. Soft but not mushy.

      Reply
  8. Debbie June 1, 2019 at 02:18

    This caramelized onion relish sounds pretty amazing . The sweet red onions cooked in butter then the balsamic vinegar is a nice touch for the relish. This is something my whole family would love for our summer cookouts.

    Reply
    1. Eva June 1, 2019 at 22:35

      This is such a simple combination of flavours, yet a winning one. Try it, you’ll love it!

      Reply
  9. Kate June 1, 2019 at 21:59

    I love the look of this relish, the color is so beautiful. And this would be quite the upgrade from ketchup and mustard on a burger!

    Reply
    1. Eva June 1, 2019 at 22:36

      Definitely! Not a healthier twist, but still a homemade condiment.

      Reply
  10. Jacqueline Debono June 2, 2019 at 11:20

    This onion relish looks delicious. I’ve never made my own but I love it. Paired with halloumi on the burger sounds a dream!

    Reply
    1. Eva June 3, 2019 at 08:58

      Yeah, halloumi is so salty that it really contrasts with the sweetness of the onion!

      Reply
  11. lauren June 2, 2019 at 13:20

    Such a fabulous idea! This would be perfect on a charcuterie board for a little sweet and savory addition! Love the addition of the balsamic too.

    Reply
    1. Eva June 3, 2019 at 08:59

      Oh yes! I have had it on a cheese board and it did a great job there, too!

      Reply
  12. Des June 3, 2019 at 03:03

    This is perfect for this weekend barbeques! It sounds like the greatest addition and would really step up my burger game.

    Reply
    1. Eva June 3, 2019 at 08:59

      And it only takes a half hour to wrap up!

      Reply
  13. Stacey June 3, 2019 at 03:16

    I’m going to have to give this a try, it sounds perfect to top off my burgers. Looks so good!

    Reply
    1. Eva June 3, 2019 at 09:00

      Thanks Stacey! Hope you enjoy!

      Reply
  14. Daniela June 3, 2019 at 07:25

    I have dreams of making a relish just like this! Such a nice summer gift too. Really inspired to make your recipe :)!!!

    Reply
    1. Eva June 3, 2019 at 09:00

      Tiny jars of this good stuff would definitely make for a great present, along with a bottle of wine, for dinner hosts!

      Reply
  15. Chef Markus Mueller June 3, 2019 at 09:44

    Caramelized onions are my favorite! My wife hates them though, which ends up working in my favor because I get to eat more lol! I have an 8 year balsamic hidden on the cupboard which will go so well with this!

    Reply
    1. Eva June 3, 2019 at 10:13

      Oh yes! There’s nothing like quality Balsamico.

      Reply

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