Set aside one fifth of the strawberries to reserve for the top decoration, choosing those that are more or less the same size. Cut the rest into a fine dice and add to a bowl. Add 2 tbsp sugar, the juice of a lemon, toss and let rest for 15 minutes.
Separate the egg whites from the yolks. Whip the whites to hard peaks, adding about 1 tbsp sugar during the last minute of whipping.
Add the rest of the sugar to the yolks and beat on medium speed until light and fluffy, 3 minutes. Add the mascarpone and continue whipping until combined, 2 minutes. Pour in one third of the limoncello, whisk until combined.
Gently fold in the whipped eff whites to the mascarpone cream until fully combined.
Drain the strawberries reserving the juice. Pour it in a shallow bowl and stir in the rest of the limoncello.
Spread an even layer of mascarpone cream over the bottom of a casserole dish.
Quickly dip the ladyfinger biscuits in the strawberry juice and limoncello mixture on both sides, then place over mascarpone cream. Repeat creating a layer of dipped biscuits. See notes for further info.
Top biscuit layer with half of the diced strawberries.
Add another layer of mascarpone cream, then proceed to create a second layer of dipped biscuits, then top with the rest of the diced strawberries. Spread a final layer of mascarpone cream on top.
Take the strawberries you had set aside and slice them lengthways. Place them over the top layer of the tiramisu covering it all. Top with powdered sugar to sweeten the top layer of strawberries. Add some lemon zest for decoration.
Cover the strawberry tiramisu with cling film. Place it in the fridge and let it rest for 2 hours or overnight.