In a large bowl combine flour, salt and baking powder. With hands cut in shortening until mixture is crumbly (similar to the texture of pie crust). Warm juice on low heat or in the microwave. Add the juice to the flour mixture and begin kneading, until all dough comes together. If the mixture is too moist add 1 tbsp of flour and continue to knead adding more flour if necessary.
Cover dough with a damp cloth and allow to rest for 15 minutes.
After dough has rested separate into 12 balls. Lightly flour your surface and begin rolling out each ball into a round, 1/8 inch thick circle. Heat skillet or cast iron Comal and cook each tortilla 1 to 2 minutes on each side.