Preheat oven to 425°F (220°C). Grease a 12-cup muffin tin or line with paper liners.

Toss blueberries with 1 tablespoon flour in a small bowl. Set aside. This prevents sinking.

In a large bowl, whisk together flour, sugar, baking powder, salt, and cinnamon.

In a separate bowl, whisk together eggs, milk, sour cream, melted butter, and vanilla extract.

Pour wet ingredients into dry ingredients and fold gently until just combined — do not overmix. A few lumps are fine.

Fold in the flour-coated blueberries until just incorporated.

Divide batter evenly among muffin cups, filling almost to the top. Sprinkle with coarse sugar.

Bake at 425°F for 5 minutes, then reduce temperature to 375°F (190°C) without opening the oven. Continue baking for 15-17 minutes until tops are golden and a toothpick comes out clean.

Cool in pan for 5 minutes before transferring to a wire rack. Best served warm.