Preheat your oven to 350°F (175°C).
In a mixing bowl, combine the blueberries, 1/2 cup of sugar, lemon juice, and vanilla extract. Gently toss to coat the blueberries and set aside to marinate for about 10 minutes.
In another bowl, whisk together the flour, remaining 1/2 cup of sugar, baking powder, and salt.
Gradually stir in the milk and melted butter until just combined. The batter will be slightly lumpy; do not overmix.
Pour the batter into a greased 9x13-inch baking dish.
Spoon the marinated blueberries evenly over the batter, but do not stir. Sprinkle the cinnamon on top.
Bake for 40-45 minutes, or until the cobbler is golden brown and a toothpick inserted in the center comes out clean.
Allow to cool for at least 10 minutes before serving.