Black Plum Cake with Lemon Filling

To make the cake: grease and flour two 20cm round cake pans

Mix together the all-purpose flour, yeast, cinnamon, and nutmeg in a large bowl

Add the plums and hazelnuts

Beat the egg whites until stiff peaks form, then add 1/2 cup granulated sugar and beat until combined

Beat the butter or margarine with the remaining 1/2 cup granulated sugar, then add 2 of the egg yolks, vanilla extract, and beat well

Alternate adding the flour mixture and milk to the egg yolk mixture, beating well after each addition

Add the filling and mix carefully

Distribute evenly into the prepared pans

Bake in a moderate oven (180°C) for 40-50 minutes or until a toothpick comes out clean

Let cool in pans for 10 minutes, then remove from pans and let cool completely

To make the filling: combine the granulated sugar and cornstarch in a small saucepan

Add the water and cook over medium heat, stirring constantly, until the mixture thickens and bubbles, about 1 minute

Remove from heat and stir in the remaining egg yolks, then return to heat for an additional minute

Stir in the butter or margarine, lemon zest, and lemon juice

Place a sheet of plastic wrap directly over the filling to prevent it from forming a skin, and let cool completely

Cut each cake in half

Distribute 1/3 of the filling over each of the three layers

Assemble the layers on a plate

Cover with the top layer without filling

Garnish with whipped cream and black plums if desired

Chill for at least 4 hours or overnight before serving, then serve in 16 portions.