A tender blueberry buckle with a buttery streusel topping and juicy berries is a charming, old-fashioned family dessert. This rustic coffee cake-style treat is perfect for brunch or dessert.
Preheat your oven to 350°F (175°C) and lightly grease an 8-inch square baking dish.
In a medium bowl, whisk together 1.5 cups all-purpose flour, baking powder, and salt for the batter.
In a large bowl, cream 0.5 cup softened butter with 0.75 cup sugar until light and fluffy, then beat in the egg and mix until just combined.
Add flour mixture to the butter mixture alternately with 0.5 cup milk, starting and ending with the dry ingredients. Gently fold in the blueberries to avoid crushing them.
Spread the batter evenly in the prepared pan.
For the streusel: combine 0.5 cup sugar, 0.33 cup flour, and 1 tsp cinnamon in a bowl. Cut in 0.25 cup cold cubed butter until crumbly using a pastry cutter or fingers.
Evenly sprinkle the streusel topping over the batter.
Bake for 45–50 minutes, or until a toothpick inserted into the center comes out clean and the topping is golden brown.
Let the buckle cool in the pan for at least 20 minutes before slicing and serving.