German Tree Cake

Instructions

1. Prepare the batter
   In a large bowl, cream together the softened butter and sugar until light and fluffy, about 5 minutes. Add vanilla extract and mix well. Add egg yolks one at a time, beating well after each addition. In a separate bowl, sift together the flour, cornstarch, and salt. Gradually fold the dry ingredients into the butter mixture. Add rum and lemon zest and mix until just combined.
2. Beat the egg whites
   In a clean, dry bowl, beat the egg whites until stiff peaks form. Gently fold the beaten egg whites into the batter in three additions, being careful not to deflate the mixture. The batter should be smooth and have a dropping consistency.
3. Preheat the broiler
   Position an oven rack about 4 inches from the broiler and preheat the broiler to high. If using a traditional Baumkuchen rotisserie, prepare it according to manufacturer's instructions. Otherwise, you'll bake individual layers under the broiler.
4. Bake the layers
   Line the bottom of a 9-inch springform pan with parchment paper. Spread a thin layer (about 3-4 tablespoons) of batter onto the bottom of the pan. Place under the broiler for 1-2 minutes until golden brown. Remove from oven, spread another thin layer of batter on top, and return to broiler. Repeat this process until all batter is used, creating 15-20 thin layers. The cake should develop characteristic rings resembling tree rings when cut.
5. Cool the cake
   Allow the cake to cool in the pan for 10 minutes, then run a knife around the edges and release the springform. Transfer to a wire rack and cool completely.
6. Apply the glaze
   Warm the apricot jam in a small saucepan until it becomes liquid. Strain through a fine-mesh sieve to remove any fruit pieces. Brush the entire cake with the warm apricot glaze and allow to set for 30 minutes.
7. Add chocolate coating
   Melt the chocolate with vegetable oil in a double boiler or microwave in short intervals, stirring frequently. Pour the chocolate over the cake, using a spatula to spread it evenly over the top and sides. Allow the chocolate to set completely before serving.