Place butter and lemonade together in a small shallow dish. Work together with a fork.
Place on an 8x12-inch sheet of wax paper. Shape into a 3/4-inch diameter log. Roll up in wax paper and chill for 1 hour or until firm.
For muffins:
Heat oven to 375 degrees.
Line 15 regular muffin cups with cupcake liners. Set aside.
In a large mixing bowl, stir together first five ingredients. Make a well in center. Set aside.
In a separate medium mixing bowl, stir together sour cream, melted butter, zest, lemonade, eggs, and extract until evenly combined.
Pour over flour mixture. Stir just until mixed. Stir in almonds.
Spoon batter into paper-lined muffin cups, filling about 2/3 full. Bake for 18-22 minutes or until tops are just golden brown and a toothpick inserted in center comes out clean.
Five minutes before muffins are done, unroll butter and slice into slightly larger than 1/4-inch thick slices.
Remove muffins from oven. Place a butter slice on each hot muffin.
Cool for 5 minutes in pan before removing from pans to wire rack. Cool for 5-10 minutes more before serving.
