1. Preferably use a stainless steel or glass bowl, but not plastic for whipping the egg whites.
2. Make sure the bowls and all the utensils are clean and dry. Even a little bit of fat from the egg yolks or another source can ruin the meringue.
3. Separate the eggs when are still cold, they separate better this way. Bring the eggs to room temperature before whipping them, so you get a nice volume.
4. Once the meringue is whipped, try to turn upside down the bowl, should not fall :)
5. Be patient with the lemon curd...takes a little bit of time to thicken.
Heat the oven to 150 degrees.
Whip egg whites together with the lemon juice until foamy. Add the sugar, spoon by spoon until fully incorporated. When all the sugar is incorporated into the mixture, add the salt. The meringue should look stiff and glossy.
With a pen draw a circle of 23cm diameter on a baking sheet. Turn over the baking sheet on the other side, and distribute the meringue to fit the shape you draw. Try to make the edges a little bit taller to leave space in the middle for the cream and decorations.
Decrease the oven temperature to 110 degrees and bake the meringue for 2h. After, leave the meringue in the oven, for another 2h, until completely cooled (do not open the door of the oven in between).
Place the sugar in a small bowl. Zest the lemons directly over the sugar, and mix well with a spatula. Add the lemon juice and salt. Combine all in a small saucepan over low-medium heat. Once the liquid start to boil, remove from the heat. The sugar should be dissolved already.
Whisk the egg yolks in another bowl. While whisking, add 1 spoon from the hot lemon and sugar mixture. Continue adding spoon by spoon until all well incorporated. In this way, the egg yolks mixture is tempered and gets progressively to a higher temperature. Move the mixture to a saucepan and heat over very low heat, stirring constantly. Do not let the mixture to boil!
After approx 10-12 minutes, the mixture will be thicker. At this point, remove from the heat and add the butter. Mix all well together and transfer to a clean bowl. Cover the bowl and let the lemon curd to cool in the fridge for 2-3 hours. Can be easily stored in the fridge, in an airtight glass container up to 1 week.
Whip the cream with powder sugar until soft and stiff. Do not use the mixer, better use a balloon whisk, not to overbeat it.
Once the meringue is ready and cooled, layer the lemon curd and the whipped cream on top, decorate with berries. Serves immediately, otherwise, the meringue will absorb the liquid from the lemon curd and cream, and will become very chewy.