If desired, partially freeze beef for easier slicing. Trim fat from beef. Thinly slice beef across the grain into thin bite-size strips. Sprinkle steak strips with 2 teaspoons of the blackened seasoning; toss to coat well.
For sauce, in a small bowl stir together the water, tomato paste, cornstarch, beef bouillon granules, and remaining 1/4 teaspoon blackened seasoning; set aside.
In a wok or large skillet heat oil over medium-high heat. Add stir-fry vegetables. Cook and stir for 2 to 3 minutes or until crisp-tender. Remove vegetables from wok. Add beef strips to hot wok. (Add more oil as necessary during cooking.) Cook and stir for 2 to 3 minutes or until desired doneness.
Push meat from center of wok. Stir sauce. Add to center of wok. Cook and stir until thickened and bubbly. Return vegetables to wok. Stir together to coat all ingredients with sauce. Heat through. Serve over rice.