Vegan Misir Wot Pierogi

Name: Vegan Misir Wot Pierogi
Ingredients: 12 ounces russet potatoes (1 large or 2 small); 1 1/2 cups red lentils, rinsed; 3 tablespoons berbere spice mix (see Cook's Note); 2 tablespoons tomato paste; 1 tablespoon onion powder; 2 teaspoons garlic powder; Salt; Vegetable oil, as needed; Instant potato flakes, as needed; All-purpose flour, for dusting; Vegan Pierogi Dough, recipe follows; Caramelized onions and sour cream, for serving; 3 1/2 tablespoons whole flax seeds; 3 tablespoons plus 1 teaspoon instant mashed potatoes; 6 cups all-purpose flour; 6 tablespoons warm water; 1 teaspoon baking powder; 1 teaspoon salt