1/2 c. butter
1 c. sugar
1 egg
1/2 c. sour cream
1 c. flour
1/2 tsp. baking powder
Pinch of salt
1 tsp. orange rind, grated

Cream butter and sugar. Blend in egg and sour cream. Add flour, baking powder, salt, and grated orange rind. Beat until smooth. Bake in greased muffin tin, 10-15 minutes at 400 degrees.

Variations (I've found many!) :

Apple: Use brown sugar in place of white sugar. Replace orange rind with 1 teaspoon cinnamon and add in 1 chopped apple.

Chocolate Chip: Use brown sugar in place of white sugar; replace orange rind with 1 teaspoon vanilla. Add in 1 cup chocolate chips.