2 tablespoons cold unsalted butter, cut into small pieces
Instructions
Preheat the oven to 375 degrees F (190 degrees C). Line a 12-cup muffin tin with paper liners.
Make the muffins: Place blueberries into a small bowl. Sprinkle 1 1/2 tablespoons flour over top and gently toss to coat.
Combine 2 cups flour, baking powder, and salt in a medium bowl.
Beat sugar and butter in a large bowl with an electric mixer until light and fluffy, 2 to 3 minutes. Beat in eggs, one at a time, then mix in vanilla and lemon zest.
Without overworking the batter, gently fold in 1/2 of the dry ingredients, then all of the milk, followed by the remaining dry ingredients. Gently fold in floured blueberries; don't stir. Spoon batter into the prepared muffin cups.
Make the topping: Whisk sugar, flour, and cinnamon together in a small bowl. Cut in butter with 2 knives or a pastry blender until mixture resembles coarse crumbs. Sprinkle topping over batter in the muffin cups.
Bake in the preheated oven until a toothpick inserted in the centers comes out clean, 20 to 25 minutes. Remove from the oven and set on a wire rack to cool.