Thinly slice onions. Add to a cast iron pan on low-medium heat. Season with salt and pepper. Cook for 30-45 minutes, stirring frequently. In last 10 minutes add 1/3 cup of water or white wine and stir to incorporate.

Increase heat on cast iron pan to medium. Sear and cook ribeyes individually for 45 seconds to one minute on each side.

Set aside to let rest.

Butter rye bread and place one piece butter side down into pan. Top with onions, 2 slices of ribeye, steak sauce, provolone, and the other piece of buttered rye bread.

Once the bottom has browned and become crisp, flip and repeat on the other side. You can add a lid to encourage the cheese to melt.