Yield: 12 muffins.

Streusel topping:
1 cup all-purpose flour
½ cup light brown sugar
½ teaspoon cinnamon
7 tablespoons unsalted butter, melted

Blueberry muffins:
1½ cups all-purpose flour + 1 tablespoon
2 teaspoons baking powder
¼ teaspoon salt
⅔ cup granulated sugar
2 large eggs, at room temperature
⅔ cup sour cream
⅓ cup vegetable oil
2 tablespoons lemon juice
1 teaspoon vanilla extract
1½ cups blueberries, fresh or frozen

Preheat oven to 400°. Prep large muffin pan with butter and flour, tapping out any extra flour.

For the streusel: In a small bowl, whisk together flour, brown sugar, and cinnamon. Add melted butter and stir with a fork until crumbly. Refrigerate until ready to use.

For the muffins: In a large bowl, stir together flour, baking powder, and salt. Set aside.

In a medium bowl, whisk together granulated sugar and eggs until combined. Whisk in sour cream, oil, lemon juice, and vanilla extract.

Fold wet ingredients into dry ingredients until just combined.

Place blueberries in a small bowl and dust with 1 tablespoon flour. Toss until all blueberries are coated with a thin layer of flour. Fold them gently into the batter.

Spoon batter into prepared muffin tins, filling ⅔ of each cup. Sprinkle tops generously with streusel topping.

Place the muffins in the oven and bake for 5 minutes, then reduce oven temperature to 375° and bake for 20 minutes or until a toothpick inserted in the center comes out clean. Cool for 5 minutes. Remove muffins from the pan and cool on a wire rack.