I only use tomato paste in this cheesy keto taco casserole recipe to reduce the carbs that would be in a can of crushed tomatoes. Tomato paste is very strong so you only need a small amount for a real tomato flavor. u003cbr/u003eu003cbr/u003eIf you do decide to add canned tomatoes to the ground beef layer you will need to cook in the frying pan for longer to allow all the liquid to evaporate and the meat to thicken, otherwise, it may be too sloppy.