Preheat oven to 350 degrees F (175 degrees C). Grease a round baking pan with 1 teaspoon butter; coat with bread crumbs.
Beat egg whites in a glass, metal, or ceramic bowl until foamy. Gradually add 2 tablespoons sugar, continuing to beat until stiff peaks form.
Mix remaining sugar, flour, cornstarch, and baking powder together in a large bowl. Sift over the beaten egg whites; fold together very gently until batter is smooth. Fold in melted butter and amaretto liqueur. Stir in half of the marzipan.
Pour batter into the prepared baking pan. Sprinkle remaining marzipan and sliced almonds on top.
Bake in the preheated oven until a toothpick inserted into the center comes out clean, 30 to 40 minutes. Cool cake completely, about 30 minutes. Invert onto a serving plate.