Gather the ingredients. Lightly grease an 8-inch square baking dish.
Place blueberries into the baking dish and mix with lemon juice and vanilla. Sprinkle with 1 cup sugar and ½ teaspoon flour, then stir in 1 tablespoon melted butter. Set aside.
Stir 1 ¾ cups flour, baking powder, and 6 tablespoons sugar together in a medium bowl. Cut in 5 tablespoons butter with a pastry blender until mixture resembles coarse crumbs.
Make a well in the center, pour in milk, and stir quickly until just moistened; you should have a very thick batter or a very wet dough. Add a splash more milk if needed. Cover and let rest for 10 minutes. Meanwhile, preheat the oven to 375 degrees F (190 degrees C).
Spoon rested batter over blueberries, leaving only a few small holes for the berries to peek through. Mix 2 teaspoons sugar and cinnamon together in a small bowl; sprinkle over the batter.
Bake in the preheated oven until golden brown on top and a knife inserted into the topping comes out clean, about 25 minutes to 35 minutes. Let cool until just warm before serving.
