Heat 1 teaspoon of the oil in a large skillet over medium-high heat. Season the steak with ½ teaspoon salt and ¼ teaspoon black pepper and cook, 3 to 5 minutes per side for medium-rare. Let rest for 5 minutes before slicing.
Meanwhile, mix together the roasted red peppers, scallions, vinegar, parsley, the remaining 2 tablespoons of oil, and ¼ teaspoon each salt and black pepper in a small bowl.
Serve the steak and greens topped with the red pepper relish.