In a medium bowl, combine 1 teaspoon of olive oil, fresh lime juice, minced garlic, ground cumin, salt, and pepper to create the marinade.
Place the 7-ounce flank steak in a shallow dish and pour the marinade over it, ensuring the meat is well coated. Let it marinate for at least 30 minutes at room temperature, or up to 2 hours in the refrigerator for deeper flavor.
Preheat your grill to medium-high heat. Meanwhile, wash the sweet potato and cut it into 1/2-inch thick rounds or wedges.
Toss the sweet potato pieces with the remaining 1 teaspoon of olive oil, a pinch of salt, pepper, and an extra sprinkle of cumin for warmth and richness.
Place the sweet potato pieces on a baking sheet and roast at 400°F for about 25-30 minutes, turning halfway through until they are tender and lightly caramelized.
Grill the marinated steak on the preheated grill for about 4-5 minutes per side for medium-rare, adjusting cooking time as needed for your preferred doneness.
Allow the carne asada to rest for 5 minutes after grilling, then slice thinly against the grain.
Plate the sliced steak alongside the roasted sweet potatoes, and garnish with a fresh squeeze of lime or a sprinkle of chopped cilantro, if desired. Serve immediately.