Preheat Oven to 350 degrees.

In a medium bowl, mix together the butter, sugar, buttermilk, egg, vanilla extract, and lemon zest.

In another bowl, mix together the flour, baking powder, baking soda, and salt.

Add the dry ingredients to the wet, and mix until smooth

Divide the batter equally between 10 paper cup lined muffin cups. Bake 18-20 minutes or until a toothpick inserted in the middle come out clean. Remove from muffin tin. Let cool completely before icing.