In a large bowl, gently toss together the blueberries, both sugars, flour, lemon juice, and lemon zest. Stir in the melted butter. Set aside.
4 cups blueberries, ¼ cup sugar, ¼ cup brown sugar, 2 teaspoons flour, 1 tablespoon lemon juice, 1 teaspoon lemon zest, 4 tablespoons butter
In another bowl, whisk together the flour, brown and white sugar, baking powder, and salt. Add the milk and vanilla, and whisk just until smooth—don’t overmix.
1 cup flour, ½ cup brown sugar, ½ cup granulated sugar, 2 teaspoons baking powder, ¼ teaspoon salt, 1 teaspoon vanilla, 1 cup milk
Pour the blueberry mixture into a heat-safe air fryer baking dish (about 7x9" or similar to fit your basket). Gently pour the batter over the berries—do not stir. Sprinkle the top with cinnamon, if desired.
Cinnamon
Place the dish into your air fryer basket. Cook at 375°F (190°C) for 15–18 minutes, or until the top is golden brown and a toothpick inserted into the batter comes out clean.
Let cool slightly. Serve warm with a scoop of vanilla ice cream or whipped cream.