Place diced onion and bell pepper in bottom of slow cooker. Trim excess fat from meat then cut into serving-sized pieces. Sprinkle meat lightly with salt and pepper.

Add flour to medium mixing bowl then dredge each piece of meat, reserving excess flour. Place meat in slow cooker on top of veggies.

Add pureed or diced tomatoes (including juice) and tomato sauce into the bowl containing remaining flour. Whisk until mixture is well combined then stir in remaining ingredients (beef broth, minced garlic, beef bouillon, paprika, pepper, mustard powder and Worcestershire). Pour over meat, stirring to ensure sauce is distributed evenly among the layers of meat and that it is completely submerged in sauce.

Cover and cook on low for 7–8 hours. When the dish has finished cooking, carefully remove meat (it will be very tender) from slow cooker then arrange on a platter. Give gravy a good stir, season to taste using salt and pepper then ladle over meat. Serve remaining gravy on the side. Yum!