Lemon Cream Cake

Method

1. Prepare the lemon custard: heat milk in a saucepan. In another bowl, beat egg yolks with sugar, add lemon juice and cornstarch. When the milk is about to boil, pour it into the egg mixture while stirring. Return everything to the heat, add lemon zest, and cook until thickened. If lumps form, whisk vigorously off heat. Pour into a shallow container, cover with parchment paper (touching the surface), and refrigerate for about 2 hours.
2. Prepare the soft shortcrust pastry: in a bowl, mix flour, baking powder, and sugar. Add cold butter cut into cubes and rub into the dry ingredients until sandy. Add eggs and lemon zest, knead into a dough. Form a flat disc, wrap in plastic wrap, and refrigerate for about 1 hour.
3. Roll out the chilled pastry on a floured surface into a circle large enough to line the tart pan. Place it in the pan, pressing the bottom and sides up to half the height. Patch any thin spots with extra pastry trimmings. Smooth the edges with a knife. Refrigerate for 10 minutes.
4. Prepare the sponge topping: whip whole eggs and extra yolk with sugar until very pale and fluffy. Add lemon zest. Sift in flour and cornstarch and fold gently. Add melted butter (cooled to room temperature) and fold until combined.
5. Assemble the cake: remove the pastry base from the fridge. Fill it with the lemon custard using a piping bag (reserve some for decoration). Level the custard. Spoon the sponge batter on top and level it. Use the reserved custard to pipe lines radiating from the center to the edge (like 8 slices). Place a lemon slice on each line.
6. Bake in a static oven preheated to 170°C (338°F) for about 55 minutes. Let cool completely before unmolding. Dust with powdered sugar before serving.