Position your oven rack in the center of your oven. Preheat oven to 400°F Prepare the muffin pans by spraying the cups and rims with nonstick spray, or just by putting the paper cups inches If you are using the silicone pans, spray as directed and then place on a baking sheet.
Whisk the flour, sugar, baking soda, baking powder, and salt in a medium bowl until well blended. Set aside.
In a large bowl, whisk the egg and buttermilk until well blended. Whisk in the lemonade concentrate, melted butter and lemon zest until smooth. Stir in the prepared flour mixture until moistened--do not overmix.
Fill the prepared tins three-quarters full. Use additional greased muffin tins, or small, ovensafe, greased ramekins for the leftover batter. Or save for a second batch.
Bake for 18 minutes, or until the muffins have lightly browned, flat tops and a toothpick inserted into one of them comes out with a crumb or two attached.
Set the pan on a wire rack to cool for 10 minutes. Gently rock each muffin back and forth to release it from the pan. Cool them for 5 minutes more before serving. If storing or freezing the muffins, allow them to cool completely before sealing in airtight containers or freezer bags. The muffins will stay fresh up to 24 hours at room temperature or up to 1 month in the freezer.