01 -
Set your oven to 350°F (175°C). Put the butter in a 9×9-inch dish and slide it into the oven for 3-4 minutes so the butter melts completely.
02 -
Grab a big mixing bowl and combine the flour, sugar, baking powder, and salt. Stir in the buttermilk, vanilla, and lemon extract if you're using it. Mix until it's smooth.
03 -
Pour the batter gently over the melted butter in the baking dish. Don’t mix it; let the butter naturally layer with the batter.
04 -
Evenly spoon the lemon filling or curd over the batter. As it bakes, the filling will sink and create a custard-like texture underneath.
05 -
Bake for 45-55 minutes until the edges are golden and puffed. The middle should look set but still soft, and a toothpick should come out mostly clean with just a few moist crumbs.
06 -
Take it out of the oven and let it rest for around 10-15 minutes. This makes the filling firm up a bit, so it’s easier to serve.
07 -
Cut it into squares while it’s still warm. Add whipped cream, powdered sugar, fresh lemon slices, or ice cream on top if you want.