Nutrition per serving may change if servings are adjusted.
¾ cup butter, softened
½ cup granulated sugar (see Tip)
1 egg yolk
⅔ cup granulated sugar (see Tip)
2 egg whites
1 tablespoon vanilla
2¼ cups all-purpose flour
¼ cup cornstarch
½ teaspoon baking powder
½ teaspoon salt
2 tablespoons powdered sugar (see Tip)
Remove zest and squeeze 6 tablespoons of juice from lemons. For lemon curd, in a medium bowl, beat 2 tablespoons of the butter and ½ cup granulated sugar with a mixer on medium just until combined. Gradually beat in ¼ cup of the lemon juice and the egg yolk. Stir in 2 teaspoons of the lemon zest (mixture may appear curdled).
Transfer mixture to a small saucepan. Cook and stir over low until smooth. Cook and stir over medium 3 minutes or until slightly thick. Transfer to a bowl. Cover surface with plastic wrap and chill at least 1 hour (curd will thicken during chilling).
Preheat oven to 350°F. Line two large cookie sheets with parchment paper.
In a large bowl, beat the remaining 10 tablespoons butter and ⅔ cup granulated sugar on medium until combined. Beat in egg whites, vanilla, 4 teaspoons of the lemon zest and the remaining 2 tablespoons lemon juice (mixture may appear slightly curdled). In a small bowl, stir together the next four ingredients (through salt). Add to butter mixture and beat just until combined. If necessary, chill dough 1 hour or until easy to handle.
Shape dough into 1-inch balls. Place 1 inch apart on prepared cookie sheets. Using your thumb, make an indentation in center of each ball.
Bake 12 to 14 minutes or until bottoms are very light brown. If cookie centers puff during baking, re-press with the back of a small spoon. Cool on cookie sheet 2 minutes. Remove; cool on wire racks. Sprinkle lightly with powdered sugar. Fill centers with lemon curd and sprinkle with additional lemon zest.
Tip: We do not recommend using a sugar substitute for this recipe.
Storage: Place cookies in a single layer in an airtight container. Store in refrigerator up to 3 days.