In a cast iron skillet heat the olive oil and butter over medium heat. Toss in the heritage ribeye steak and cook over medium heat until golden brown. Be sure to move them around from time to time to be sure they are fully cooked. Once they are cooked transfer them to a bowl. Set aside.
Slice the tomatoes, onion and lettuce, set aside.
Slice the ciabatta bread in half.
Spread the edges of the cut sides of the bread with the mayonnaise.
Layer the lettuce on top of the mayonnaise, and follow with the tomatoes, onions, cooked steak and cheese.
Press the top of the loaf firmly on the sandwich, then tightly wrap in foil.
Place on a baking sheet and bake in the oven for 15 minutes or until cheese is melted.
Open the foil for the last few minutes to lightly toast the bread.