Ingredients:

1 cup unsalted butter
1/2 cup confectioners' sugar
1/2 teaspoon almond extract
2 cups arrowroot flour
6 egg whites
1/2 teaspoon cream of tartar
1/3 cup confectioners' sugar for decoration

Directions:

Preheat oven to 350 degrees F (180 degrees C). Thoroughly butter the bottom and sides of a 13 x 9 inch baking pan. In a large mixing bowl, cream together the butter and sugar. Beat in the almond extract. Gradually mix in the arrowroot flour. In a separate bowl, beat the egg whites and cream of tartar until stiff peaks form. Gently fold the egg whites into the batter. Pour the batter into the baking pan and smooth the surface with a rubber spatula. Bake for 30 minutes, or until a toothpick inserted in the center comes out clean. Dust with confectioner's sugar.