Set a rack in the lower third of the oven and preheat to 375 degrees.

Grease a 9- or 9.5-inch pie plate or baking dish.

In a food processor fitted with the metal blade, process the egg yolks, sugar, vanilla, lemon zest and ricotta and process until smooth. Scrape down the sides of the food processor and add the egg whites. Process for 30-60 seconds to blend well and to incorporate some air into the mixture

Pour the mixture into the pie plate and bake for 15 minutes. Sprinkle the blueberries on top and bake until set and springy, about 20-25 more minutes. Let cool slightly and serve.