Melt the salted butter in a pot over low heat and set aside. It needs to reach room temperature before use.
In a bowl combine flour, baking powder and baking soda and set aside.
In another bowl grate the zest of the lemons and combine it with the sugar. Stir well in order to rub the essential oils of the lemon zest right into the sugar. The sugar should get a bit wet. Set aside.
Crush the dried lavender and add it to the sugar mix.
Pour the Greek yoghurt into the sugar mix and mix it in with a hand mixer at medium-slow speed.
Always mixing, add the lemon juice and the eggs, one at a time.
Stop the mixer and add the flour mixture in. Give it a first stir with the mixer off, then start the mixer and whisk the powders in at low speed.
Lastly, whisk in the melted butter. Make sure it has reached room temperature, as you don't want to be adding it warm.
Pour cake batter into a loaf pan and bake in the preheated oven at 180°C for 45 minutes, or until a toothpick inserted in the centre comes out clean.