Preheat the oven to 350°F (175°C).

In a mixing bowl, combine blueberries, sugar, lemon juice, and cornstarch. Stir gently to combine.

Pour the blueberry mixture into a greased baking dish.

In another bowl, whisk together flour, sugar, baking powder, and salt.

Add milk and melted butter to the dry ingredients and stir until just combined.

Pour the batter over the blueberry filling in the baking dish.

Bake in the preheated oven for 30-35 minutes, or until the topping is golden brown.

Let cool for a few minutes before serving.