Roast beef, whether previously cooked or not, can be a tough cut of meat, depending on its quality. However, there are numerous things you can do to soften the meat, some of which alter and enhance the flavour of the meat and some of which preserve its original taste. While softening roast beef is fairly simple, it does take some time, so you'll want to start the process the day before you cook the roast or early in the morning if you are preparing dinner.
Place the roast beef in a large container with a tight-fitting top. Pour enough sweet liquid like orange juice or soda over the top of the roast beef to fully cover the meat by 1 inch. Place the roast beef in the refrigerator to marinate for eight hours or overnight. The sugar in the liquid will soften the meat by helping the meat to release moisture.
Fill a flavour injector with a 20-to-one mixture of fresh, clean water and kosher salt or sea salt. Inject the liquid slowly into the centre of the roast beef right before cooking. Allow the meat to rest for 20 minutes so the salt solution can move throughout the whole roast.
Slice cooked roast beef and place it in a container with a tight-fitting top. Cover the roast beef with soda water and add any fresh or dried herbs you want to use to season the meat. Place the meat in the refrigerator for 24 hours to soften and take on the herb flavour.
Marinate the roast beef in vegetable juice or beef broth for 12 hours in a large container with a tight-fitting top. Alternately, you can slow-roast roast beef in a crock-pot or slow cooker using vegetable juice or beef broth.
When using a flavour injector to soften roast beef, you may want to use a little less salt than usual if you rub the outside of the meat since you are injecting some salt directly into the meat. Common herbs and seasonings for marinating roast beef include marjoram, thyme, cayenne pepper, rosemary and basil.