Preheat your oven to 350°F / 176°C and grease a 10" / 26cm pan or line it with parchment paper.
Combine the white chocolate and milk/cream in a microwave-safe bowl.
1 cup + 3 tablespoons (200 grams) chopped white chocolate, 2 tablespoons whipping cream or milk
Heat in 30-second increments and stir after every 30 seconds. Set aside to cool while you prepare the rest.
Beat the butter with 100 grams of sugar (ignore the amount shown below - it's a technical issue I can't fix) and beat until fluffy.
3/4 cup + 1 tablespoon (180 grams) unsalted butter, 2/3 cup (133 grams) granulated sugar
Add the lemon zest, egg YOLKS (also ignore that it says eggs below - you just want the yolks here) and lemon extract and beat until well combined. Then add the almond flour and the melted chocolate. Add the limoncello / lemon juice and beat until combined.
3 cups + 3 tablespoons (320 grams) finely ground blanched almond flour, 2 tablespoons lemon zest, 4 large eggs, 1 teaspoon lemon extract, 2 tablespoons limoncello
In a separate bowl with spotlessly clean beaters, beat the egg whites until soft peaks form. Gradually add the remaining 30 grams of sugar to the egg white mixture. Fold the egg whites into the almond batter until well combined. Spoon the batter into the greased pan and bake for 40 - 45 minutes. If making half the cake, use a 7" / 18cm pan and bake for 30 minutes. The cake will puff up in the oven, but when cooling, it'll fall back down.
Let it cool completely in the pan and then invert the cake onto a plate, and then flip that back into the pan or onto another plate (so that it's not upside down). Sprinkle on some powdered sugar if desired and top with berries, but only before serving. Cake can be stored at room temperature for up to 3 days or refrigerated (I think it's best that way) for up to 5.