1/2 cup (1 stick) unsalted butter room temperature, plus more for muffin tin
1 1/2 cups all-purpose flour plus more for muffin tin
2 teaspoons baking powder
1/2 teaspoon salt
1/2 cup low-fat buttermilk or plain low-fat yogurt
1 teaspoon vanilla extract
Zest of 1 lemon finely grated, plus juice, plus 2 tablespoons more lemon juice for the glaze
1 cup granulated sugar
2 large eggs
1 1/2 cups confectioners' sugar
Preheat oven to 350 degrees. Butter and flour a 6-cup jumbo muffin tin. In a medium bowl, whisk the flour with the baking powder and salt. In a small bowl, whisk together the buttermilk, vanilla, and lemon zest and juice of 1 lemon. Set aside.
With an electric mixer, cream butter and granulated sugar until light. Add eggs one at a time, beating well after each addition. With mixer on low speed, add flour mixture in three batches, alternating with two additions of buttermilk mixture.
Divide evenly among muffin cups. Bake until a toothpick inserted in center of a cake comes out clean, 20 to 25 minutes. Cool 10 minutes in tin, then cool completely on a rack.
Set rack over wax or parchment paper. In a small bowl, stir confectioners' sugar with remaining lemon juice until smooth. Pour over cakes, spreading to edges with a small knife. Let set 30 minutes.