In a large baking dish, add olive oil, soy sauce, red wine vinegar, garlic, salt and pepper. Whisk with a fork.
Pound each steak on both sides with a meat mallet. Dip one by one into marinade, coating on both sides. Arrange in the same dish in a few layers laying flat, cover with plastic wrap and marinate for 2 hours or up to overnight in the fridge.
Preheat cast iron skillet on medium-high heat and add 2 steaks. No need to add oil as steaks are marinated in it. Pan fry for 2-3 minutes per side, depending on the thickness of the steak, marinating time and how you like it done. I find cutting into the center with a knife is the most accurate way to tell if it's ready. My steaks were too thin for an accurate thermometer reading.
Transfer onto a platter and cover with the foil while you are cooking remaining steaks. Steaks will keep cooking with residual heat and keep warm. Make sure to cover the last batch of steak with foil and let them rest 2 minutes.
Serve with mashed potatoes or rice and a salad.
Notes
Store: Refrigerate in an airtight container for up to 4 days. Reheat by simmering on low heat in the pot on the stove or in a microwave.
Freeze: Freeze in an airtight container for up to 3 months. Thaw in the fridge overnight.
Reheat: These steaks are thin and dry out fast. Reheat in a microwave or in a skillet on low heat until heated through.