(Adapted from Martha Stewart)
Makes one 9-inch cake
Unsalted butter, room temperature, for pan
3/4 cup sugar, plus more for pan
1 1/2 pounds fresh whole-milk ricotta cheese, pureed in a food processor until smooth
6 large eggs, separated
1/4 cup all-purpose flour
Finely grated zest of 2 limes, plus juice
1/4 teaspoon salt
Preheat oven to 375 degrees F. Generously butter and sugar a 9-inch springform pan (3 inches deep). Whisk together ricotta, egg yolks, flour, 6 tablespoons sugar, the lime zest and juice, and salt in a large bowl.
Whisk egg whites with a mixer on low speed until foamy. Raise speed to high, and gradually add remaining 6 tablespoons sugar, whisking until stiff, glossy peaks form, 3 to 4 minutes. Gently fold a third of the whites into ricotta mixture using a rubber spatula until just combined. Gently fold in remaining whites until just combined.
Pour batter into pan, and bake until center is firm and top is deep golden brown, about 1 hour. Let cool on a wire rack for 10 minutes. Run a knife around edge of cake; release sides to remove from pan, and let cool completely.
Let stand at room temperature for 20 minutes before serving.
