Preheat the oven to 300 degrees. Set a rack in the middle level. Butter and flour a 9½-inch springform pan and tap out the excess flour.
Place the ricotta in a large mixing bowl and stir it as smooth as possible with a rubber spatula.
Stir the sugar and flour together and stir them thoroughly into the ricotta. Stir in the eggs one at a time, then the remaining ingredients.
Pour the mixture into the prepared pan and bake the gattò from about 1¼ to 1½ hours, until it is a light golden color, fairly firm in the center, and the point of a sharp knife inserted 1 inch from the center emerges without any batter clinging to it. Cool the gattò on a rack in a draft-free place; it will sink slightly as it cools. Cover the gattò with plastic wrap and chill until serving time. Before serving, release the sides of the springform pan but leave the gattò on the pan base.