Flank Steak with Smoky Roasted Potatoes

Heat oven to 425 degrees F. On a large rimmed baking sheet, toss the potatoes and red pepper with 2 tablespoons oil, 1 tablespoon paprika, and 1/2 teaspoon each salt and pepper. Arrange in an even layer and roast, turning once or twice, until the potatoes are golden brown and tender, 20 to 25 minutes. Meanwhile, heat the remaining 2 teaspoons oil in a large skillet over medium-high heat. Season the flank steak with 1/2 teaspoon each salt and pepper and cook to desired doneness, 5 to 7 minutes per side for medium-rare. Transfer to a board and let rest for 5 minutes before slicing. In a small bowl, whisk together the mayonnaise, lemon juice, mustard, and remaining 1 teaspoon paprika. Toss the potatoes and red pepper with the scallions and serve with the steak and dipping sauce.