Place Chuck roast in crock pot. Pour Tomato sauce and onions over roast.
Cover and cook on high for 5 hours or on low for 10.
Open Crock pot, Meat should fall right off of the bones. Remove bones from crock pot.
Remove half of the meat for another dish. *See Note
Mix in a single packet of taco seasoning to remaining meat. Cook on low for 15min. Stir in can of Refried beans. Leave mixture on low until ready to serve.
Serve on Tortillas, and top with Cheese, Salsa, lettuce, whatever your heart desires.
This makes a ton of burritos! Very Filling!
Notes
*If you would like to use all of the meat to make the burrito filling use 2 packets of taco seasoning and 2 can of Refried beans.