Slow-Cooked Steak Fajitas

1 1/2 lb. beef flank steak
1 can diced tomatoes with garlic and onion (undrained)
2 garlic cloves, minced
1 tsp. ground coriander
1 tsp. ground cumin
1 tsp. chili powder
1/2 tsp. salt
1 medium onion, sliced
1 medium green pepper, julienned
1 medium sweet red pepper, julienned
1 Tbsp. minced fresh cilantro
2 Tbsp. cornstarch
1 Tbsp. water
12 flour tortillas warmed
Sour Cream
Salsa

Thinly slice steak across the grain into strips; place in a 5 quart slow cooker. Add tomatoes, garlic, coriander, cumin, chili powder, and salt. Cover and cook on LOW for 6 hours. Add onion, peppers, and cilantro. Cover and cook 1 to 2 hours longer or until meat is tender. Combine cornstarch and water until smooth. Gradually stir into slow cooker. Cover and cook on HIGH for 30 minutes or until slightly thickened. Serve mixture on tortillas w/ sour cream and salsa.