Directions

1. Preheat oven to 450, with racks set in upper and lower thirds. Place pork on a rimmed baking sheet. Rub with 1 teaspoon oil; season with cumin, salt, and pepper. Roast on upper rack until an instant-read thermometer inserted in the thickest part of meat registers 145 degrees, 35 to 40 minutes. Remove from oven, and cover loosely with aluminum foil; let rest about 10 minutes. (Slice off 1/3 of meat and refrigerate.)
2. About 15 minutes after pork has begun roasting, place sweet potatoes on another rimmed baking sheet; drizzle with 2 tablespoons oil. Season with red-pepper flakes (if using), salt, and pepper; toss to coat. Roast on lower rack, until tender, tossing once during cooking, 25 to 35 minutes.
3. In a large bowl, whisk lime juice with remaining 2 tablespoons oil; season with salt and pepper. Add sweet potatoes, beans, onion, and, if using, cilantro; mix gently to combine. Thinly slice pork, and serve with salad and lime wedges.