Preheat the oven to 400°F. Line and butter two 8-inch cake pans.

Mix the egg yolks, ½ cup of the sugar, the butter, flour, cornstarch, baking powder, baking soda, and lemon zest in a processor. Add the lemon juice and milk and process again.

Divide the mixture between the prepared pans. You will think you don’t even have enough to cover the bottom of the pans, but don’t panic. Spread calmly with a rubber spatula until smooth.

Whisk the egg whites and cream of tartar until peaks form and then slowly whisk in the cup of sugar. Divide the whisked whites between the two pans, pouring or, more accurately, spreading the meringue straight on top of the cake batter. Smooth one flat with a metal spatula, and with the back of a spoon, peak the other and sprinkle 1 teaspoon sugar over the peaks. Put the pans into the oven for 20–25 minutes.

With a cake-tester, pierce the cake that has the flat meringue topping to check it’s cooked all through. (It will have risen now but will fall back flattish later.) No sponge mixture should stick to the tester. Remove both cakes to a wire rack and let cool completely in the pans.

Unmold the flat-topped one onto a cake stand or plate, meringue side down. Whisk the heavy cream until thick but not stiff and set aside. Spread the flat sponge surface of the first, waiting, cake with the lemon curd and then spatula over the cream and top with the remaining cake, bronze-peaked meringue uppermost.