Butter and flour a 12-inch springform mold. Preheat the oven to 300°F (150°C). In a mixer, beat the eggs, sugar, and vanilla bean on high speed for 20–22 minutes until firm and airy.
Sift the flour and corn starch together twice. Gently fold the dry mixture into the eggs with a rubber spatula until fully incorporated.
Pour the batter into the mold and bake for 45 minutes. Use a toothpick to check doneness. Cool completely before slicing.
Prepare the pastry cream and add the zest of one lemon. Whip the cream with a bit of sugar and the zest of two lemons.
Cut the cake horizontally into 3 layers. Fill the first and second layers with pastry cream using a piping bag. Cover the cake with whipped lemon cream.
Decorate the top with alternating strips of pastry cream and lemon whipped cream. Best served fresh within two days, covered and refrigerated.
