Combine 1 Knorr® Beef flavor Bouillon Cube and next 3 ingredients. Rub steak with spice mixture; set aside.
Cook garlic in a large nonstick skillet over medium-high heat about 10 minutes or until garlic is tender and skin is golden, turning occasionally. Remove garlic; peel and finely chop; set aside.
Brown steak over high heat. Remove steak and warm. Add onion and tomatillos and cook over medium-high heat about 4 minutes or until onion is tender. Stir in water, remaining bouillon cube, peppers and reserved garlic and bring to a boil. Return steak to skillet, reduce heat and simmer about 5 minutes or until steak is desired doneness.