01 - In a large mixing bowl, whisk together gluten-free flour blend, salt, and baking powder until evenly distributed.
02 - Add cold cubed butter to flour mixture and use a pastry cutter or fork to blend until the mixture forms coarse crumbs.
03 - Add one egg, apple cider vinegar, and cold water to the bowl. Mix until dough begins to form. If the dough appears dry, add extra water, one tablespoon at a time, until just cohesive. Shape into a disc, wrap in plastic, and refrigerate for 30 minutes.
04 - Heat olive oil in a skillet over medium heat. Add finely chopped onion and minced garlic, sautéing for about 3 minutes until softened.
05 - Add diced red bell pepper, ground cumin, smoked paprika, dried oregano, and optional chili powder. Season with salt and pepper and cook for 2 minutes until fragrant.
06 - Stir in shredded chicken breast and tomato sauce. Cook for 3 to 4 minutes, stirring to ensure the mixture heats through and slightly thickens. Remove from heat, then fold in chopped green olives and cilantro or parsley. Allow filling to cool to room temperature.
07 - Preheat oven to 400°F. Line a large baking sheet with parchment paper.
08 - Lightly dust a work surface with gluten-free flour. Roll chilled dough to approximately 1/8-inch thickness. Using a 4- to 5-inch round cutter, cut out circles.
09 - Place 2 tablespoons chicken filling in the center of each dough circle. Fold the dough over to form a half-moon, gently pressing edges to seal. Crimp edges with a fork for a secure closure.
10 - Arrange empanadas on the parchment-lined baking sheet. Beat the remaining egg and lightly brush the tops of each empanada. Bake for 20 to 25 minutes or until pastry is golden. Let cool slightly before serving.