In second mixing bowl, combine flour, baking powder, baking soda and salt. Mix together. Gradually spoon dry ingredients into the sour cream mixture and beat at low speed until smooth. Fill each muffin pan halfway with batter.

Make topping by mixing together sugar, flour, cinnamon and butter with a fork. The topping should look pebbly. Sprinkle a little bit of mixture on top of each muffin.

Reduce oven to 350 degrees and bake approximately 25 minutes or until a toothpick inserted in center comes out clean. Remove and cool.