This recipe from First Lady Michelle Obama was featured on NPR's All Things Considered:
1 1/2 cups unsalted butter, softened
1 1/2 cups plus 2 tablespoons sugar
2 egg yolks
3 cups cake flour (not self-rising)
1 teaspoon each orange and lemon zest
2 tablespoons amaretto (almond liqueur)
1/4 teaspoon salt
1 beaten egg white
Chopped nuts or dried fruit (optional)
Preheat oven to 325 degrees. Mix together butter and 1 ½ cups of sugar.
Add egg yolks one at a time and beat until smooth. Stir in flour, zest, amaretto and salt, and mix only until everything is incorporated. Spread dough evenly onto baking pan and brush top of dough with egg white and remaining 2 tablespoons of sugar. Sprinkle with nuts or fruit if desired. Bake until golden brown, approximately 25 minutes. Cool for a short time, then cut while still warm.
from VPR Cooks