Melt 1 1/2 tablespoons butter in heavy large skillet over medium-high heat. Season chicken with salt and pepper. Add to skillet and cook until golden brown and cooked through, about 3 minutes per side. Transfer to platter.
Melt remaining 1 1/2 tablespoons butter in same skillet over medium heat. Add onion, mushrooms and bell pepper to skillet and sauté until almost tender, about 5 minutes. Add tomatoes with juices, broth, chili powder and crushed red pepper. Cook until mixture thickens, breaking up tomatoes with wooden spoon, about 8 minutes. Return chicken and any juices on platter to skillet. Simmer until chicken is just heated through, about 2 minutes. Transfer to platter and serve.
