3 1/2 cups all-purpose flour
1 1/2 cups granulated sugar
4 1/2 teaspoons baking powder
1 teaspoon baking soda
1 teaspoon kosher salt
2 cups buttermilk, shaken
1/4 pound (1 stick) unsalted butter, melted and cooled
1 1/2 teaspoons grated lemon zest
2 extra-large eggs
2 cups fresh blueberries (2 half-pints)
For the streusel topping:
3/4 cup all-purpose flour
1/2 cup light brown sugar, lightly packed
1 teaspoon ground cinnamon
1/4 teaspoon kosher salt
4 tablespoons 91/2 stick) cold unsalted butter, diced
Preheat the oven to 375 degrees. Line muffin tins with paper liners.
Sift the flour, sugar, baking powder, baking soda, and salt in a large bowl and blend with your hands. In a separate bowl mix together the buttermilk, butter, lemon zest, and eggs. Stir the buttermilk mixture into the flour mixture with a fork, mixing just until blended. Fold the blueberries into the batter. Don't overmix! With a standard (2 1/4-inch) ice=cream scoop or large spoon, scoop the batter into the prepared cups, filling them almost full.
For the topping, place all the ingredients in the bowl of a food processor fitted with the steel blade and pulse until the butter is in very small pieces. Pour into a bowl and rub with your fingers until crumbly. Spoon about 1 tablespoon of the streusel on top of each muffin. Bake the muffins for 20 to 25 minutes, until golden brown.