Lemon Semifreddo Cake

Instructions

1. Line the bottoms and sides of two 5 x 9-inch loaf pans with parchment paper; set aside.
2. Using a serrated knife, trim all edges of the vanilla sheet cake by 1 inch so it measures 8 x 12 inches.
3. Slice the cake widthwise, through the top, into 3 vertical pieces, each 4 x 8 inches.
4. Split each piece in half, slicing horizontally through the crumb.
5. You should have six 4 x 8-inch layers.
6. Set aside.
7. Make the semifreddo: In a large heatproof bowl set over a pan of simmering water, whisk together the egg yolks, 1/2 cup granulated sugar, and 2 tablespoons confectioners sugar until smooth.
8. Add the wine, 1/2 cup lemon juice, and lemon zest; cook, stirring constantly with a wooden spoon, and scraping across the bottom to prevent the mixture from sticking to the bowl, until the mixture is thick enough to coat the back of the spoon, 6 to 7 minutes.
9. Remove from heat, and transfer to a large bowl.
10. Let cool to room temperature (or place the pan in an ice-water bath, stirring occasionally).
11. When the custard has cooled, combine the cold water, 1/2 cup granulated sugar, and remaining teaspoon lemon juice in a small saucepan.
12. Bring the mixture to a simmer over medium heat.
13. Cook until the mixture is slightly thickened and registers 240F on a candy thermometer, about 8 minutes; wash down the sides of the pan with a pastry brush dipped in water to prevent crystals from forming.
14. Remove from heat, and let the mixture cool 2 to 3 minutes.
15. Meanwhile, in the bowl of an electric mixer fitted with the whisk attachment, beat the egg whites and remaining tablespoon sugar on medium-high speed until stiff but not until dry peaks form.
16. With the mixer still running, slowly drizzle the syrup mixture into the egg whites; continue beating until the meringue has cooled slightly and the bowl is cool to the touch.
17. In another large mixing bowl, whip the cream with the remaining 3 tablespoons confectioners sugar until soft peaks form.
18. Fold the whipped cream into the cooled lemon mixture; fold in the egg white mixture.
19. The mixture should be very smooth.
20. Place the rum in a small bowl.
21. Fit one of the cake layers in the bottom of each prepared loaf pan.
22. Using a pastry brush, lightly moisten the top of the cake with rum.
23. Using an offset spatula, evenly spread 1 1/2 cups lemon filling over each.
24. Repeat the process, making another layer of cake, rum, and filling; cover each with one of the remaining cake layers.
25. Place in the freezer at least 5 hours or overnight.
26. Just before serving, remove the pans from the freezer, and turn the cakes out of the pans; remove the parchment paper.
27. Slice into pieces.
28. Preheat the oven to 350F.
29. Line a 9 x 13-inch baking pan with parchment paper, and set aside.
30. Sift together the flour, salt, and baking powder in a medium bowl.
31. In the bowl of an electric mixer fitted with the whisk attachment, beat together the egg yolks and sugar on medium-low speed until light and fluffy.
32. Beat in the water and vanilla bean scrapings.
33. Add the dry ingredients in 3 batches, scraping down the sides of the bowl with a rubber spatula as needed, just until the flour mixture is incorporated after each addition.
34. In another mixing bowl, beat the egg whites until stiff but not until dry peaks form; whisk one-quarter of the egg whites into the batter to lighten.
35. Fold in the remaining egg whites, and pour the batter into the prepared pan.
36. Bake until the cake springs back when gently pressed in the center, 15 to 20 minutes.
37. Transfer to a wire rack to cool completely.