Put these ingredients into a large jar, pushing down until covered with the vinegar. As the veggies shrink, add vinegar to keep them covered, if needed. Rest for 2 hours or a few days in the refrigerator.

When ready to make sandwich, heat a large cast iron skillet to medium-high with 1 1/2T oil. Working in batches, saute a handful of the veggies for 3-4 minutes at a time and then set aside. Cook 1/4 of your beef at a time. Once your beef is cooked to your fineness, add 1/4 of the veggies to the beef and mix together. Then top with 3-4 slices of cheese and let it melt. Do this for each sandwich. Use a spatula to put the mixture on your bread.