Melt the butter in a medium saucepan. Add onion and bell pepper and sauté until translucent. Add bulgur and vermicelli. Salt and pepper to taste. Pour in hot beef broth. Add tomatoes and stir well. Heat oven to 350° F. Place pilaf in an oiled oven-proof baking dish, cover and bake at 350° F for 30 to 35 minutes.