Genoa's dome-shaped sponge cake soaked in rum and filled with zabaione cream. This rare mediterranean dessert is a cherished Ligurian family tradition.
Preheat oven to 350°F and lightly butter a dome or bowl-shaped cake mold.
Prepare the sponge: Separate eggs; beat whites until stiff in a clean bowl, then beat yolks with sugar until thick and pale. Fold flour, then melted butter and vanilla extract into yolks, then gently incorporate the whites for maximum lightness.
Pour batter into the mold; bake for 25-30 minutes until golden and a tester comes out clean. Let the sponge cool completely before unmolding.
While the cake cools, make the zabaione: In a heatproof bowl, whisk egg yolks, sugar, Marsala wine, and lemon zest over simmering water, whisking constantly until thick and creamy. Let cool, then fold in whipped unsalted butter for silkiness.
Carefully slice the sponge cake horizontally into 3 thin layers. Brush each layer generously with rum and milk mixture. Spread half of the zabaione cream between each layer, stacking them to reform the dome. Chill for at least 2 hours.
Before serving, sift powdered sugar over the top for a snowy finish. Slice with a sharp knife, using care to highlight the creamy layers and moist texture.