Boil chicken with enough water to cover. Cook until done. Cool & de-bone chicken. Chop chicken, and reserve broth. If you use boneless breasts, add 2-3 teaspoons chicken bouillon to water when cooking chicken.
Sauté the tomato and onion until soft. Add chicken & sauté 2 minutes. Add enough reserved broth to cover chicken mixture by about 1 inch. Season with salt, pepper, garlic powder, and comino. Simmer 15 minutes. Thicken with flour & water whisked together. Spoon out gravy into separate pan and keep warm.
Soften corn tortillas in enough hot oil to coat tortillas. Fill each softened tortilla with chicken and place in rolled tacos in dish. Spoon gravy over tacos to serve.