ursting with fresh blueberries and topped with a buttery streusel, this dessert is perfect for any time of day. Pair it with a scoop of vanilla ice cream for next-level deliciousness!
Preheat your oven to 375°F (190°C). Lightly spray a 9-inch square baking pan with nonstick cooking spray or line it with parchment paper for easy removal.
In a medium bowl, whisk together the flour, baking powder, and salt.
In a large stand mixer bowl with a paddle attachment, cream the white sugar and softened butter on medium speed until light and fluffy.
Beat in the egg and vanilla extract, scraping the sides of the bowl as needed.
Add the flour mixture to the wet ingredients in two batches, alternating with the milk. Mix on low speed until just combined. (Just like muffins, you don't want to overmix the batter.)
Gently fold in the fresh blueberries with a rubber spatula to avoid breaking them. Pour the batter evenly into the prepared pan.
In a small bowl, mix the brown sugar, flour, and cinnamon. Cut in the chilled butter with a pastry cutter, two forks, or your fingertips until the mixture forms coarse crumbs. Sprinkle the topping evenly over the batter.
Bake for 35–40 minutes, or until the top is golden brown and a toothpick inserted into the center comes out clean.
Allow the buckle to cool slightly in the pan before slicing. Serve warm or at room temperature for the best texture and flavor.