Preheat oven to 375℉.
Using a KitchenAid stand mixer or hand mixer, first mix together flour, sugar, salt, and baking powder.
2 cups all purpose flour, 1 ¼ cups granulated sugar, ½ teaspoon salt, 2 teaspoons baking powder
Then, add butter, lemon zest, eggs, milk, and vanilla extract and mix just until all ingredients are incorporated together.
½ cup salted butter, softened, 1 teaspoon lemon zest, 2 eggs, ¾ cup milk, 1 teaspoon vanilla extract
Finally, by hand, gently fold blueberries into batter.
2 cups blueberries
Spoon batter into a well greased or lined muffin pan, filling each cup about two-thirds.
Bake for 20-25 minutes. The muffins will start to rise by this time.
In the meantime, make the streusel topping. In a bowl, mix together melted butter, flour, brown sugar, and a pinch of salt. Toss together using a fork until small crumbs form.
4 tablespoons salted butter, melted, ¼ cup all purpose flour, ½ cup light brown sugar, packed, Pinch of salt
Remove muffins from oven, gently brush the top of each muffin with butter, and sprinkle with streusel topping.
Bake another 20 minutes or until a toothpick inserted in the center comes out clean. Enjoy!