Directions

1. Position racks in upper and lower thirds of oven; preheat to 450°F. Coat 2 large rimmed baking sheets with cooking spray.
2. Slice sweet potatoes crosswise into 1/4-inch-thick slices. Cut each slice into 1/4-inch-wide fries. Toss with 2 tablespoons oil in a large bowl; add paprika, cumin, salt and pepper and toss again. Divide the fries between the prepared baking sheets, spreading evenly. Bake on the upper and lower racks, stirring the fries and switching the pans halfway, until browned and tender, 25 to 28 minutes.
3. Meanwhile, combine yogurt, blue cheese and chives in a small bowl.
4. When the fries are halfway done, heat the remaining 1 tablespoon oil in a large cast-iron skillet over medium-high heat until hot but not smoking. Sprinkle steak with Montreal steak seasoning and cook, turning once, until browned on both sides, 2 to 4 minutes per side for medium. Let rest on a clean cutting board for 5 minutes. Slice crosswise into 1/2-inch-thick pieces and serve with the sweet potato fries and sauce, garnished with more chives, if desired.