2/3 cups sorghum flour
1/3 cup arrowroot starch
Rounded 1/4 teaspoon xanthan gum
1/4 cup powdered sugar
1/2 teaspoon baking powder
1/4 teaspoon salt
1/2 cup (1 stick) butter, softened
2 teaspoons lemon peel (zest), grated
2 tablespoons freshly squeezed lemon juice
1 cup sugar
Small amount sifted powdered sugar
Preheat oven to 350 degrees.
Whisk together sorghum flour, arrowroot starch, xanthan gum, powdered sugar, baking powder, and salt. Pour into an 8 x 8-inch pan; then use your fingers to incorporate butter, distributing it so that dry ingredients are moistened. Press into bottom of pan, pushing shortbread mixture slightly up the sides. Bake at 350 degrees for 20 minutes, until lightly browned (convection oven: 325 degrees for 15 minutes).
Prepare topping while base bakes. Beat lemon zest, lemon juice, eggs, and white sugar for about three minutes. Pour over cooked base and return to oven. Do not use convection oven, as temperature is too low to set eggs. Bake at 350 degrees for 22-25 minutes, until a finger touching the top will leave an impression. Mixture should be set, but you cannot test for doneness with an inserted toothpick.
When cool, sift powdered sugar over top, and cut into bars. Refrigerate. Freezes well. Yield: 16 bars.