The ultimate cinnamon crumb coffee cake muffins, moist, crunchy, and packed with flavor. A delicious treat for breakfast or brunch.
To make the muffins:
In a medium bowl, sift together flour, baking powder, baking soda, and salt. Set aside. In a standing mixer fitted with the paddle attachment, beat together butter and sugar on medium speed until light and fluffy, about 3 minutes. Scrape down the sides and bottom of the bowl as necessary. Add the egg and beat until combined. Beat in vanilla extract. Reduce mixer speed to low. Add half of the dry ingredients and beat just until combined. Beat in sour cream, followed by the other half of the dry ingredients and beat only until combined.