Place butter in 9-inch square baking dish. Set in the oven until butter is melted.
Meanwhile, in a large bowl, stir together flour, sugar, buttermilk, vanilla, and lemon zest or extract. Just stir until combined. If you stir too much the crust on the cobbler will be tough.
Pour batter over melted butter. Do not mix.
Pour lemon pie filling over batter. Do not mix.
Bake for 55 to 60 minutes. The crust will be golden and the filling will still be a little jiggly.