How to Make It
In a small bowl, combine the cilantro, jalapeño, vinegar, 2 tablespoons of the oil, and ¼ teaspoon each salt and black pepper.
Heat the remaining teaspoon of oil in a small saucepan over medium heat. Add the onion and ¼ teaspoon each salt and black pepper and cook, stirring occasionally, until tender, 4 to 5 minutes. Add the cumin and cook until fragrant, 30 seconds. Add the corn and cream and cook, stirring occasionally, until slightly thickened, 3 to 4 minutes more.
Heat grill to medium-high. Season the steak with ½ teaspoon each salt and black pepper. Grill, turning once, to the desired doneness, 2 to 5 minutes per side for medium-rare. Let rest for 5 minutes before slicing. Serve with the cilantro sauce, creamed corn, tortillas, and radishes.