Lemon Salt Lemon Cupcakes

Name: Lemon Salt Lemon Cupcakes
Ingredients: 1 stick unsalted butter, at room temperature; 1 cup sugar; 3 large eggs; 1½ cups Jeanne's gluten free all-purpose flour; 1 teaspoon baking powder; ½ teaspoon salt; ½ cup buttermilk; zest and juice of one lemon; 3 egg yolks; 1/2 cup sugar; 1/4 cup water + 1 tablespoon lemon juice; 1 1/2 sticks unsalted butter, at room temperature; zest of a lemon