Preheat the oven to 400 degrees F. Grease 8 cups of a 12-cup standard muffin pan with a little melted butter or oil and fill the remaining 4 cups with water. Sift the flour, baking powder and sugar into a large mixing bowl, stir in the lemon rind and make a well in the center.
Whisk the buttermilk, vanilla and eggs together. Add the egg mixture and the melted butter to the well in the dry ingredients. Using a metal spoon, stir until the mixture is just combined. Do not overmix - the mixture should be lumpy.
Spoon the mixture into 8 cups of the muffin pan, filling each cup about three-quarter full. Bake for 10-12 minutes, or until a skewer comes out clean when inserted into the center of a muffin. Cool in the pan for 5 minutes before lifting out onto a wire rack.
TO MAKE FROSTING: Beat the butter and cream cheese with an electric mixer until smooth. Add the confectioners' sugar and lemon juice, and beat until thick and creamy. Spread the frosting over the muffins when they are completely cold. Decorate the top of the frosting with shreds of lemon zest for a tangy flavor.
Recipe reprinted by permission of Tuttle Publishing/Periplus Editions. All rights reserved