Steps

• Beat the eggs in a stand mixer or with an electric hand mixer together with the sugar, the pinch of salt and the lemon zest.

  The mixture should be voluminous, pale and frothy; this will take about 12–15 minutes. Gently fold in the sifted flour and the potato starch, a little at a time, using a spatula and lifting motions from bottom to top.

  Pour the batter into two previously buttered and floured 22 cm (about 8.7 in) springform pans. Bake in a static (conventional) oven preheated to 356°F for 20–25 minutes; do the skewer test. Remove from the oven and let warm slightly before unmolding; then cool on a tray or wire rack.

• Split the vanilla pod lengthwise and scrape out the seeds with a small knife. Put the milk and the vanilla pod into a saucepan, place over low heat and heat until it reaches a boil.

  Put the vanilla seeds with the egg yolks and sugar in a bowl and whisk well. Add the starches and the pinch of salt. Pour the egg mixture into the hot milk and whisk. Cook, stirring constantly, for about 5 minutes over low heat until thickened.

  Remove from the heat and pour into a cold bowl. Cover with plastic wrap so that it touches the surface and cool quickly in an ice bath, then transfer to the refrigerator for at least 3 hours.

• Pour the cream into a bowl with the powdered sugar and the seeds from the vanilla bean. Whip with an electric mixer at high speed until the cream becomes glossy and semi-whipped. Keep refrigerated.

• Pour 1/3 of the semi-whipped cream into the bowl with the pastry cream and whisk to loosen the cream and make it homogeneous. Then add another 1/3 of the whipped cream and fold it in gently with a spatula using lifting motions so as not to deflate it. Once incorporated, add the remaining cream using the same method. Keep refrigerated, covered with plastic wrap, until ready to use.

• Mix the limoncello with the pineapple juice and set aside.

• Set aside 4 pineapple slices and chop the rest into pieces about 1 cm (about 3/8 in).

  Cut each sponge cake in half horizontally to make two layers; remove the outer crust with a knife. Place one layer on a serving plate.

  Brush the base with the limoncello-pineapple juice mixture and cover with 1/3 of the cream. Add half of the chopped pineapple. Place the second sponge layer on top, brush with the syrup and spread another 1/3 of the cream and the remaining chopped pineapple.

  Top with the last sponge layer. Lightly brush the top layer and cover the entire cake with the remaining cream.

  Crumble the remaining sponge cake. Decorate the cake with the crumbs and the reserved pineapple slices on the surface. Chill in the refrigerator for at least 4 hours.