In a bowl, combine lime juice, olive oil, minced garlic, cumin, salt, and pepper, then add flank steak to coat. Marinate for 30 minutes, then remove from the marinade and pat lightly so it grills with visible browning.

Preheat the grill to high heat and place flank steak on the grates. Grill for 4-5 minutes per side until the outside is well marked and the center is just cooked to your preference.

Transfer steak to a cutting board and let it rest. Rest for 5 minutes so juices redistribute, then slice against the grain.

In a bowl, mix grilled corn kernels, mayonnaise, sour cream, cotija, lime juice, and chili powder. Stir until creamy and speckled, with corn pieces coated in the sauce.

Warm corn tortillas on the grill or in a dry pan until pliable. Heat just until warm through with light spots, then keep covered.

Fill each tortilla with sliced grilled steak and spoon over elote mixture. Add cilantro and serve with lime wedges so each taco gets a fresh lime squeeze at the table.