Preheat oven to 375 degrees F (190 degrees C). Position rack in center of oven. Line muffin pan with paper liners, or butter or spray, with a non stick cooking spray, 12 - 2 3/4 x 1 1/2 inch muffin cups.
Mix together in a large bowl, egg, buttermilk, oil, and vanilla extract.
n another large bowl combine the flour, sugar, baking powder, baking soda, salt, and zest. Gently mix in berries and gently mix dry ingredients being careful not to over mix.
Using cupcake wrappers, make medium sized muffins, filling almost full with batter.