In a mixing bowl, combine all-purpose flour and salt, then cut in the cold vegan butter until the mixture resembles coarse crumbs. Stir in the apple cider vinegar and gradually add cold water until a soft dough forms. Shape the dough into a disk, wrap it in plastic wrap, and chill in the refrigerator for at least 30 minutes to firm up.

Heat olive oil in a skillet over medium heat, then sauté the chopped onion and minced garlic until translucent, about 3-4 minutes. Add diced carrot, chopped celery, and red bell pepper, cooking for an additional 5-6 minutes until softened. Stir in cooked lentils, tomato paste, and spices, cooking until heated through. Remove from heat and let the filling cool completely.

Once the dough has chilled, divide it into equal portions. Roll each piece into a 5-inch circle on a floured surface. Place a spoonful of filling in the center, fold the dough over to create a half-moon shape, and seal the edges with a fork.

Preheat your oven to 375°F (190°C). Arrange the sealed empanadas on a lined baking sheet, brush with plant milk, and bake for 25-30 minutes, or until golden brown.

While the empanadas are baking, prepare the chimichurri sauce by combining parsley, garlic, olive oil, red wine vinegar, and crushed red pepper in a food processor. Blend until well combined.