Whisk 1 1/4 cups granulated sugar,1/4 cup light brown sugar, 2 tablespoons flour and 1/2 teaspoon salt in a bowl. Whisk 1/2 cup room-temperature buttermilk, 4 room-temperature eggs, 6 tablespoons cooled melted butter, the zest and juice of 1 lemon and 1 teaspoon vanilla in a separate bowl; whisk in the sugar mixture. Pour into a 9-inch graham cracker crust and bake at 350 degrees F until golden and just set, about 45 minutes; let cool. Dust with confectioners' sugar.
Recipe courtesy of Food Network Magazine