Begin by creating a marinade with the sea salt, chopped parsley, crushed garlic, apple cider, olive oil, beef stock, chopped thyme, and crushed black peppercorns.
Place the eye of round steak in a bag, pour in the marinade, and seal. Let the steak marinate for a few hours, or preferably overnight.
Once the steak is well-marinated, heat butter and vegetable oil in a skillet over medium-high heat.
Add the marinated steak to the skillet. Sear the steak on each side until browned.
Once the steak is browned, add your choice of vegetables to the skillet. Saute the vegetables until they soften.
After the vegetables have softened, pour the leftover marinade (or additional beef stock if needed) into the skillet. Bring this mixture to a boil.
Once boiling, reduce the heat to the lowest possible setting, cover the skillet, and let it simmer for about two hours. This slow, wet heat will help break down the connective tissues in the steak, making it more tender.
After the two hours of simmering, your steak should be tender and ready. Serve with the veggies and some of the pan juices for added flavor.