To make the cake: In a large bowl, add the butter, sugar, egg yolks, and vanilla and, with a wire whisk, whisk until smooth.
250 grams unsalted butter, 250 grams granulated sugar, 6 eggs, 1 teaspoon pure vanilla extract
In a small, microwave-safe bowl, add the marzipan and amaretto and heat in the microwave in 10 second increments until warmed.If you don’t have a microwave, do this in a small saucepan. Whisk until smooth, then stir into the butter mixture. 100 grams marzipan, 45 milliliters amaretto
In a medium bowl, sift together the flour, cornstarch, and baking powder. Working one tablespoon at a time, whisk the flour mixture into the butter mixture until a thick batter is formed and no more clumps are visible.
150 grams all-purpose flour, 100 grams cornstarch, 14 grams baking powder
In a large bowl, whisk the egg whites and a pinch of salt until stiff peaks form. Fold into the batter until just combined.
1 pinch salt
To the prepared springform pan, add about ½ cup (weight: 4½ ounces or 130 g) of batter and, using a small, offset spatula, spread it into an even layer and bake until the top starts to turn golden-brown, 3 to 4 minutes.Repeat this process, carefully adding and spreading each layer, until the batter is gone (I end up with 9 layers). Make sure to keep a close eye on your cake as it can burn easily. Insert a cake tester or a toothpick into the center of the cake, if it doesn’t come out clean (a few crumbs are desirable, but no wet batter), adjust the oven control to 350°F (18° C) on the conventional setting and bake until the cake is cooked through, 5 to 7 minutes (make sure to test after 5 minutes).
Transfer to a wire cooling rack and let rest until cool enough to handle, about 5 minutes. Run a thin knife around the cake to loosen it from the pan, then carefully remove the springform ring.Cover with a clean kitchen towel and set aside to cool completely.