This is the recipe that my Grandmother handed down to me. I always make it during blueberry season. My guests just love it!
1 ½ cups white sugar
½ cup butter, softened
2 large eggs
4 cups all-purpose flour
4 teaspoons baking powder
½ teaspoon salt
1 cup milk
4 cups fresh blueberries
Preheat oven to 375 degrees F (190 degrees C). Grease a 9×13-inch baking pan.
Prepare buckle: beat sugar and butter in a bowl using an electric mixer until creamy and smooth. Beat in eggs. Whisk flour, baking powder, and salt together in a separate bowl. Stir flour mixture into creamed butter mixture, alternating with milk, until batter is just combined; fold in blueberries. Pour batter into the prepared pan.
Prepare topping: combine sugar, flour, and cinnamon together in a bowl. Cut in cold butter using a pastry blender or 2 knives until topping is crumbly. Sprinkle topping over batter.
Bake in the preheated oven until a toothpick inserted into the center comes out clean, 40 to 45 minutes. Cool buckle on a wire rack.