Steak and Potato Salad

1 teaspoon lime juice
1 teaspoon chili powder
1/4 teaspoon salt
1 clove garlic, mashed into a paste
8 ounces sirloin steak, trimmed
3/4 pound small potatoes
2 tablespoons sherry vinegar (I used Worcestershire sauce because I hate vinegar)
1 tablespoon olive oil
1/2 teaspoon ground cumin (I left this out)
1/4 teaspon salt (I left this out too)
1/4 teaspoon freshly ground pepper
3 scallions, thinly sliced
1/4 cup chopped fresh cilantro

Mix 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. Grill the steak, turning once, until an instant-read meat thermometer inserted into the thickest part registers 140°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 salt in a large bowl. Add the steak and any accumulated juices, the potatoes, scallions and cilantro; gently toss to coat.

Source: adapted from http://www.eatingwell.com/recipes/steak_purple_potato_salad.html