Cake Preheat oven to 350°F. Butter and flour a 9 inch springform pan. Onto a sheet of waxed paper, sift together the flour, baking powder and salt and set aside. In a large bowl, cream the butter with an electric mixer on high until light. Gradually add the sugar and continue beating until the mixture is very light and fluffy. With mixer on medium add eggs, one at a time, beating well after each addition, then beat in the vanilla and almond extracts.
Changing to a low speed alternately beat in the sifted dry ingredients and milk, beginning and ending with the dry ingredients and beating only until combined. Pour the batter into the prepared pan, smoothing the top even. Topping Combine the almonds, sugar, butter and cream in a small saucepan and cook over moderate heat until the butter melts. Pour the topping over the cake batter, spreading lightly.
Bake until the top of the cake is golden or until toothpick inserted in the center comes out clean, and the cake shrinks from the side of the pan, about 40 minutes. Cool the cake in the pan on a wire rack for 20 minutes. Loosen around the sides of the pan with a sharp knife, and remove carefully. Cool the cake completely. Filling Combine 2/3 cup of the milk with the sugar and salt in a small heavy saucepan and bring to a boil over moderate heat.
Pour the remaining milk into a small bowl; beat in the cornstarch, then the egg yolks. Whisking constantly, add a little of the hot milk to the egg yolk mixture. Bring the remaining milk in the saucepan back to a boil over moderate heat. Whisking constantly, pour the tempered eggs into the saucepan. Cook, whisking constantly, until the mixture comes to a boil. Lower the heat and simmer for one minute longer. Immediately remove the saucepan from the heat, stir in the amaretto and vanilla and almond extracts, and pour the custard into a small bowl.
Immediately cover the surface of the custard with plastic wrap. Refrigerate until cold, up to 24 hours. Assembling the Cake Whip the cream for the custard filling until it forms soft peaks. Stir about 2 tablespoons of the whipped cream into the chilled custard, then fold in the remainder. Slice the cake in half crosswise and place the bottom half, cut side up on a serving platter. Gently spread the custard filling on the cake, then top with remaining cake layer, cut side down. Refrigerate the cake until serving time. Dust lightly with confectioners sugar just before serving.