Preheat oven to 350 degrees F (175 degrees C). Grease a 9-inch round cake pan.
In a medium bowl, cream together the butter and sugar until light and fluffy. Beat in eggs one at a time, then stir in the baking powder, baking soda, salt and vanilla.
Stir in the flour alternately with the buttermilk. Spread the batter into the prepared pan.
In a separate bowl, mix together the blueberries, brown sugar, walnuts, flour and melted butter. Sprinkle over the top of the cake.
Bake for 40 minutes in the preheated oven, until a toothpick inserted in the center of the cake comes out clean.
Allow cake to cool before serving.
Interesting Facts
The cake originated in the 1800s by the Blubaugh family in Pennsylvania.
The name “buckle” comes from the fact that the topping “buckles” when it bakes.
The cake can be made with any type of berry or fruit.