01 - Combine flour and salt in a large bowl. Cut in chilled butter until the mixture resembles coarse crumbs. Stir in egg, cold water, and vinegar until a dough forms. Knead briefly, wrap in plastic wrap, and refrigerate for 30 minutes.
02 - Heat olive oil over medium heat in a skillet. Sauté onion for 2 to 3 minutes until translucent. Add minced garlic and cook for 30 seconds. Add ground beef, breaking it up, and cook until browned.
03 - Incorporate cumin, smoked paprika, chili powder, oregano, salt, pepper, and tomato sauce. Simmer the mixture for 5 minutes to thicken. Remove from heat and allow to cool before stirring in shredded cheddar and Monterey Jack cheeses.
04 - Set oven to 400°F and line a baking sheet with parchment paper.
05 - On a floured surface, roll dough to approximately ⅛-inch thickness. Cut out 5-inch diameter circles using a cutter or a glass.
06 - Place about 2 tablespoons of filling in the center of each dough circle. Fold dough over to create a half-moon shape and crimp the edges with a fork to seal completely.
07 - Arrange filled empanadas on the prepared baking sheet and brush each with beaten egg to enhance browning.
08 - Bake in the preheated oven for 22 to 25 minutes or until golden brown. Allow to cool slightly before serving.