Preheat your oven to 375°F (190°C) and line a 12-cup muffin tin with paper liners or grease thoroughly.
Toss your 1½ cups of blueberries with 2 tablespoons of flour in a small bowl to coat them evenly.
In a medium bowl, whisk together the 2 cups flour, baking powder, and salt.
In a large bowl, beat the softened butter and sugar with an electric mixer until light and fluffy, about 2-3 minutes.
Add eggs one at a time, beating well after each addition. Stir in sour cream, lemon juice, lemon zest, and vanilla extract.
Gradually add the dry ingredients to the wet ingredients, alternating with milk. Begin and end with the dry ingredients. Mix just until combined.
Gently fold in the flour-coated blueberries using a rubber spatula.
If using streusel topping, combine all streusel ingredients in a small bowl and mix with a fork or your fingers until crumbly.
Fill each muffin cup about ¾ full with batter. If using streusel, sprinkle it evenly over the tops.
Bake for 22-25 minutes or until a toothpick inserted in the center comes out clean or with just a few moist crumbs.
Allow to cool in the pan for 5 minutes before transferring to a wire rack to cool completely.