Lemon Meringue Pie--Gluten Free

Gluten free pie crusts were the bane of my existence. I was especially irked because I had just recently decided upon the perfect flaky pie crust recipe with wheat flour, and that, of course, just didn't work with gluten free flours. Finally, my good friend Melissa told me that the best thing is to use the Gluten Free Pantry mix. Which is excellent. But, I had a panic last Thanksgiving when I was slated to bring pies for our dinner, and the stores were out of the mix. Mel had to bale me out by sharing hers with me. I decided then that I would no longer have to rely on a mix to make a great pie crust. So, I tried a few more recipes from scratch, only to be totally disappointed. Since the mix is so great, I've used it as a template for a recipe from scratch. I also don't personally need to make 4 pie crusts at a time, so this is what I've created, adjusting the ingredients to make one double crust:
1 cup rice flour
1/4 cup potato starch
1/4 cup corn starch
1 Tbsp sugar
1/2 tsp xanthan gum
1/2 tsp salt
1/4 tsp baking powder
5 Tbsp butter flavored shortening
5 Tbsp unsalted butter
1 egg, beaten
1 Tbsp ice water
1 1/2 tsp cider vinegar

Mix together dry ingredients in a medium bowl. Cut butter and shortening into small pieces and cut into dry mixture, until it forms chunks the size of peas. In a small bowl, combine wet ingredients. Add all at once to mixture and, using a fork, combine until it forms a ball. Chill for one hour. Divide the ball in half and roll out in between two pieces of wax paper, or plastic wrap.

Lay out and press into pie plate. Poke bottom of pie crust and bake at 425 for 12 minutes, until golden brown. Set aside to cool.
Filling

3 eggs, separated
1 1/2 cups sugar
3 Tbsp GF flour
3 Tbsp cornstarch
dash salt
1 1/2 cups water
2 Tbsp butter
finely shredded peel from one lemon
1/2 cup lemon juice

Set egg whites aside for meringue. Mix sugar, flour, cornstarch and salt in medium saucepan. Gradually stir in water, cook over medium-high heat, stirring constantly until mixture is thickened and bubbly. Reduce heat; cook and stir two minutes more. Remove from heat. Slightly beat egg yolks in small bowl with a fork, gradually add about 1 cup of the thickened mixture in with the yolks. Pour egg yolk mixture into remaining hot filling in saucepan. Bring to a gentle boil. Cook and stir 2 minutes more. Remove from heat. Stir in butter and lemon peel. Gently stir in lemon juice. Keep filling warm while preparing meringue.

3 egg whites
1/2 teaspoon vanilla
1/4 teaspoon cream of tartar
6 Tbsp sugar

In a large glass mixing bowl, combine egg whites, vanilla and cream of tartar. Beat with an electric mixer on medium speed about 1 minute or until soft peaks form.
Gredually add sugar, one tablespoon at a time, until the sugar dissolves and forms stiff, glossy peaks.

Pour lemon filling into pie shell. Immediately spread meringue over hot filling, carefully sealing to edge of pastry to prevent shrinkage. Use the edge of the knife to create peaks in the meringue. Bake at 350 for about 15 minutes, or until the peaks of the meringue are a golden brown.

Cool for about an hour, then transfer to the refrigerator and chill for 3-6 hours before serving (so the filling properly sets up).