A delicious slow cooked beef roast with a tomato and onion gravy is a delicious way to have dinner ready when you get home and it is a heart meal the whole family will love.
Trim fat and connective tissue from beef chuck roast if needed. Place roast in large crock pot fat side up and season roast with salt and pepper.
Spread onion wedges over top of the roast.In measuring cup whisk together tomato sauce, water, horseradish, mustard, salt and pepper. Pour over top of the roast and onions.
Cover crock pot and turn on heat. Cook time on low is 8-10 hours or 4- 6 hours on high setting.
Remove roast from crock pot and strain broth. Remove as much fat as possible from top of broth.
In a small bowl, whisk 2 tablespoons flour and 3 tablespoons water until smooth. Place broth in a medium saucepan and bring to a boil. Whisk flour/water mixture into boiling broth whisking constantly until thickened.