To prepare a steak onion and pepper fajitas recipe, you will first need to prepare the steak. Cut your steak into 12 inch thick slices. Slice your peppers and add them to the skillet. Heat your skillet over medium-high heat. Add your onion slices and cook them until they are soft, about 5 minutes. Remove the onions from the pan and set them aside. In the same skillet, heat your olive oil. Once the oil is hot, add in your chopped steak and onion. Cook them for 2 to 3 minutes, or until the meat is no longer pink in the center. Then add your diced tomatoes, green onions, jalapeos, and cilantro. Toss everything together until everything is evenly coated.