01 -
Preheat oven to 375°F. Line a muffin tin with paper liners.
02 -
In a small bowl, whisk together flour, sugar, and cinnamon. Pour in melted butter and mix with a fork until crumbs form. Chill in refrigerator.
03 -
In a large bowl, whisk together flour, sugar, baking powder, salt and citrus zest.
04 -
In another large bowl, whisk together melted butter, egg, and buttermilk. Don't worry if it looks curdled.
05 -
Add wet ingredients to dry ingredients. Stir just until batter comes together - it should be thick and lumpy. Do not overmix.
06 -
Fold in blueberries gently until evenly distributed. Avoid overmixing to prevent purple batter.
07 -
Using a 3-tablespoon cookie scoop, divide batter between 12 muffin cups.
08 -
Break up chilled crumb topping with fingers and sprinkle over muffin batter.
09 -
Bake for 28-30 minutes until crumbs are golden brown and muffin springs back when lightly pressed.
10 -
Can be enjoyed warm, but flavor is best after cooling for about 2 hours.