In a mixing bowl, toss blueberries with lemon juice and 1/2 cup sugar. Pour into a greased 8x8-inch baking dish.
In another bowl, whisk together flour, baking powder, and salt. Stir in milk, melted butter, and vanilla until just combined.
Spoon the batter evenly over the blueberries. Sprinkle the top with 1 tablespoon sugar.
Bake for 30 minutes, or until the topping is golden and the blueberries are bubbling.
Let cool slightly before serving—preferably with a scoop of vanilla ice cream!