Heat oven to 375°F. Place butter in a 9x13-inch dish to melt while preheating.
Toss blueberries with the first portion of sugar, cornstarch, lemon zest, and lemon juice. Rest 5 minutes.
Whisk flour, the second portion of sugar, baking powder, and salt in a bowl.
Pour in milk and vanilla. Whisk just until smooth and pourable.
Remove hot pan. Swirl melted butter to coat the bottom evenly.
Pour batter into the buttered pan. Do not stir.
Spoon blueberry mixture evenly over the batter. Do not stir.
Sprinkle cinnamon over the top. Bake 38–42 minutes until deep golden and bubbling.
Cool 10 minutes before serving. Enjoy warm, plain or with vanilla ice cream.
Notes
Variation: Swap in 2 cups sliced peaches for part of the berries, or use frozen blueberries without thawing (add 1 extra teaspoon cornstarch). Store leftovers covered at room temperature for 1 day or refrigerate up to 3 days; warm briefly in a 300°F oven to refresh.This recipe is an original creation inspired by classic Easy Blueberry Cobbler Recipe flavors. All ingredient ratios and instructions are independently developed.