c (2 sticks) unsalted butter
c firmly packed light brown sugar
t vanilla extract
c sifted flour
Preheat oven to 325. Butter a 9" round cake pan. Beat the butter, brown sugar, and vanilla together until fluffy. Add the flour in 4 batches, combining well after each addition. (You may do this with your hands.) Scrape the dough into the prepared pan with a spatula and pat into an even layer. Prick the surface of the dough all over with a fork. Score in wedges with a knife before baking (don't cut all the way through the dough). Bake in the upper third of the oven for about 30 minutes, or until top is puffy and lightly browned.