Rich orange-flavored pastry cream is sandwiched between layers of meringue-topped yellow cake in this decadent dessert. Martha made this recipe on "Martha Bakes" episode 713.
Preheat the oven to 350 degrees. Lightly butter two 9-by-2-inch round baking pans. Dust with flour, tapping out excess. Set aside.
Make the cake: Place butter, sugar, salt, and egg yolks in the bowl of an electric mixer fitted with the paddle attachment. Beat on medium speed until combined. Reduce speed to low. Beat in flour, buttermilk, vanilla, and baking powder, until well blended.
Divide batter between prepared pans (the batter will barely cover the bottom of the pans).
Make the meringue topping: In a clean bowl of an electric mixer fitted with the whisk attachment, whisk the egg whites until soft peaks form. While continuing to whisk, gradually add 1 cup sugar and whisk until meringue is smooth, glossy, and somewhat stiff, but not holding a stiff peak.
Spread the meringue on top of the cake batter, and sprinkle evenly with almonds, cinnamon, and remaining tablespoon sugar. Bake cakes until lightly browned, about 30 minutes. Transfer pans to a wire rack to cool for 15 minutes. Loosen the edges with a knife or offset spatula, gently remove cakes from pans, and return the rack to cool completely. If some of the almonds fall off during this process, sprinkle them back on top.
Make the filling: Whisk together sugar, cornstarch, and salt in a medium saucepan. Whisk together milk, orange juice, and egg yolks in a glass measuring cup. Add milk mixture to the saucepan, along with butter. Cook over medium heat until mixture comes to a simmer. Continue to cook until it comes to a boil. Let boil 1 minute. Remove from heat and add vanilla.
Strain pastry cream through a fine-mesh sieve into a bowl. Stir in orange zest and cover with plastic wrap, pressing it directly onto the surface of the pastry cream to prevent a skin from forming. Refrigerate until chilled, at least 2 hours or up to 2 days. Just before using, whisk until smooth.
Place one of the cake layers, meringue-side up, on a serving plate. Spread with pastry cream. Top with second cake layer, meringue-side up. Serve immediately or refrigerate until serving, up to 3 hours.