Heat oven to 400 degrees F. Coat rimmed baking sheet with nonstick cooking spray. Place sweet potatoes on baking sheet and toss with 1 tablespoon of the canola oil and season with salt, paprika and pepper. Bake at 400 degrees F for 20 to 25 minutes until tender, turning once.
Meanwhile, heat remaining tablespoon oil in a large nonstick skillet over medium-high heat. Add flank steak and stir-fry for 4 minutes; remove to a plate. Add onion, peppers, garlic and cumin; stir-fry for 6 minutes. Stir in soy sauce, vinegar and tomatoes; bring to a simmer.
Stir beef with any accumulated juices, sweet potatoes and cilantro into the skillet. Heat gently and serve over cooked brown rice.
