First, chop the onion, tomatoes, and jalapeños into long slices. Next, heat the skillet with 4 tablespoons of olive oil. Once the skillet is heated, saute the onion and jalapenos for 2 minutes. Next add 2 pounds of chopped skirt steak and season your steak with 2 tablespoons of fajita seasoning. Add in the tomatoes and the tomatillo sauce and let the ingredients simmer until fully cooked.