Steak and Purple-Potato Salad

Mix lime juice, chili powder, 1/4 teaspoon salt and garlic in a small bowl to form a paste; rub onto both sides of steak. Refrigerate the steak.

Place potatoes in a large pot, cover with water and bring to a boil over high heat. Cook until tender when pierced with a fork, 15 to 20 minutes, depending on the size of the potatoes. Drain, let cool for 10 minutes, then quarter.

While the potatoes cool, preheat grill or grill pan over medium-high heat. Oil the grill rack or pan (see Tip). Grill the steak, turning once, until an instant-read meat thermometer inserted into the thickest part registers 140 degrees F, about 10 minutes total on the grill or 16 to 20 minutes in a grill pan. Let rest for 5 minutes, then cut into 1/4-inch-thick slices.

Whisk vinegar, oil, cumin, pepper and the remaining 1/4 teaspoon salt in a large bowl. Add the steak and any accumulated juices, the potatoes, radishes, scallions and cilantro; gently toss to coat.