Corsican-Style Cheesecake

Strain ricotta through cheesecloth or in a fine-mesh sieve for 1 hour. Preheat oven to 350°. Butter an 8'' square baking pan. Line bottom of pan with buttered parchment paper and set aside. Whisk together eggs, sugar, strained ricotta, and lemon zest in a medium bowl. Pour into prepared pan. Bake until dark brown on top and a toothpick inserted in center comes out clean, about 1 hour and 15 minutes. Allow to cool 20 minutes; run a knife around sides of pan, turn out on large plate, peel off paper, then turn cake face up.