How to Make It
In a medium bowl, whisk the flour with the granulated sugar. Gradually whisk in the milk followed by the ricotta, eggs and lemon zest. Strain the mixture through a fine sieve set over a bowl. Cover and refrigerate overnight.
Preheat the oven to 450°. Place a 9- to 10-inch cast-iron skillet in the oven to heat for 10 minutes.
Whisk the pancake batter briefly. Carefully remove the skillet from the oven and swirl in the butter to coat. Add the pancake batter to the hot skillet, scatter the blueberries in the center and bake until puffed, set and browned at the edge, 17 to 20 minutes. Dust with confectioners’ sugar and serve immediately.