Mix flour, baking powder and baking powder in a large bowl. Cut in butter until mixture resembles coarse crumbs then make a well in center of mixture.
Beat egg in a small bowl; add sugar, lemon zest, lemon juice, sour cream and milk.
Add to flour mixture, mixing just until moistened.
Spoon into greased muffin pans until cups are about 2/3 full. Or grease pans and the surface around the pan as well, filling cups all the way, this will produce muffins with larger tops, though less muffins.