Step 1

Preheat oven to 375 degrees. Generously butter and sugar a 9-inch springform pan (3 inches deep). Whisk together ricotta, egg yolks, flour, 6 tablespoons sugar, the zest, and salt in a large bowl.

Step 2

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.

Step 3

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. Serve with citrus-vanilla compote.