Gugelhupf is a versatile Viennese specialty that can be made by many methods in different sizes and flavors. The original version is a sweet yeast dough, but when baking powder became available, some (but not all) cooks embraced the new, easy-to-use leavening. This classic version uses yeast, but it is more of a beaten batter than a kneaded dough, and it makes a very moist and rich cake, perfect for an afternoon Jause. The egg whites give this dough a lovely light texture.
1ounce (½cube) fresh compressed yeast or 3¾teaspoons (about 1½envelopes) active dry yeast
1cupmilk (heated to 110° to 115°F if using dry yeast)
12tablespoons (1½sticks) unsalted butter, at cool room temperature
For the sponge: Crumble the yeast into the milk in a medium bowl and add the sugar. Let stand 3 minutes. Add the flour and whisk until smooth. Cover with plastic wrap and let stand in a warm place until bubbly and doubled in volume, about 30 minutes.
For the dough: Beat the butter and sugar in the bowl of a heavy-duty standing mixer fitted with the paddle blade on high speed, until light in color and texture, about 2 minutes. Add the sponge, and then beat on low speed. Add the egg yolks, one at a time, then the rum, vanilla, lemon zest, and salt. Gradually mix in enough of the flour to make a soft dough that barely leaves the sides of the bowl. Let the dough mix for a minute or two before deciding to add more flour—it takes time to come together. Beat with the paddle blade until smooth, occasionally scraping the dough off the blade, about 5 minutes.
Beat the egg whites in a grease-free medium bowl with a handheld electric mixer on high speed until stiff peaks form. Before adding the whites to the batter, scrape all of the batter off the paddle blade. On low speed, gradually beat the whites into the dough until they are incorporated. The whites will deflate, and the dough will become a batter. Mix in the raisins.
Generously butter a 9- to 9½-inch Gugelhupf or fluted tube pan. Sprinkle the almonds in the pan, pressing them to adhere to the sides. Spread the batter evenly in the pan. Place the pan in a large plastic bag. Put a tall glass of hot water in the bag next to the pan so the plastic doesn’t touch the top of the pan, and close the bag. Let stand in a warm place until the dough fills the pan by three quarters, about 1 hour.
Position a rack in the center of the oven and heat to 350°F. Bake for 30 minutes. Cover the top of the pan loosely with aluminum foil to prevent overbrowning. Continue baking until the top is golden brown and an instant-read thermometer inserted in the loaf reads 200°F, about 30 minutes more. Cool on a wire rack for 10 minutes. Unmold onto the rack and cool completely. Sift generously with confectioners’ sugar before serving.