- 1 cup cake flour
- 1 teaspoon baking powder
- 1/8 teaspoon salt
- 1 stick (4 ounces) unsalted butter, at room temperature
- 1 1/4 cups plus 2 teaspoons sugar
- 4 large eggs, separated, at room temperature
- 3 tablespoons milk
- 1 teaspoon pure vanilla extract
- 1/3 cup sliced almonds (about 1 ounce)
- 2 large eggs
- 1 large egg yolk
- 1/3 cup Key lime juice (see Note) or fresh lime or lemon juice
- 3/4 cup sugar
- 1 teaspoon cornstarch
- Pinch of salt
- 4 tablespoons cold unsalted butter, cut into 4 pieces
- Assemble the cake Preheat the oven to 350°. Line the bottoms of two 8-by-2-inch round cake pans with wax paper and grease the paper.
- Sift together the flour, baking powder and salt. In a large bowl, using an electric mixer, cream the butter with 1/2 cup of the sugar until fluffy. Add the egg yolks and beat for 2 minutes. In a measuring cup, stir together the milk and vanilla; beat the milk into the butter in two batches, alternating with the dry ingredients, until just incorporated. Scrape the batter into the prepared pans (the batter will barely reach up the sides of the pan).
- In another large bowl, using clean beaters, beat the egg whites at medium speed until they hold soft peaks. With the machine on, gradually sprinkle in 3/4 cup of the sugar and beat until the whites are glossy, 3 to 4 minutes. Gently spread the meringue over the cake batter in the pans; do not smooth the tops. Sprinkle the almonds, then the remaining 2 teaspoons sugar, on the meringue.
- Bake the cakes in the bottom third of the oven for 25 minutes, or until the meringue is puffed and lightly browned. Transfer the pans to racks and let the cakes cool completely; the tops will sink considerably.
- Place the whole eggs and egg yolk in a heatproof bowl and whisk. In a medium nonreactive saucepan, bring the lime juice, sugar, cornstarch and salt to a boil over moderate heat, whisking. Gradually whisk the mixture into the eggs. Scrape the lime curd into the saucepan and cook over moderate heat, stirring with a wooden spoon, until thick enough to coat the spoon, about 5 minutes; do not boil. Remove from the heat and stir in the butter.
- Strain the curd into a clean bowl. Let cool at room temperature briefly, whisking occasionally; then press a piece of wax paper directly on the surface and refrigerate until chilled, at least 2 hours or overnight.
- Run a knife around the sides of the cake layers to loosen them from the pans. Carefully invert the layers onto baking sheets; remove the wax paper. Invert one layer onto a cake platter. Spread all the lime curd on top. Cover with the other cake layer, meringue side up. To serve, slice gently with a serrated cake knife.
The cake can be refrigerated for up to 1 day; loosely cover with plastic wrap.
If you are lucky enough to find fresh Key limes, use them. Otherwise, you can purchase bottled Key lime juice at specialty food stores or from The King Arthur Flour Baker's Catalogue, 800-827-6836.