Preheat your grill to medium-high heat. If using frozen corn, thaw and drain it before using.
In a bowl, combine the corn kernels, olive oil, chili powder, smoked paprika, garlic powder, salt, and pepper. Toss to coat evenly.
Grill the corn mixture in a grill basket or on a sheet of aluminum foil for about 10-12 minutes, stirring occasionally, until charred and tender.
While the corn is grilling, season the flank steak with salt, pepper, and lime juice. Grill the steak for about 4-5 minutes per side for medium-rare, or until desired doneness. Remove from the grill and let it rest for 5 minutes before slicing.
In a small bowl, mix the mayonnaise, lime juice, and chili powder to create a creamy sauce.
Warm the corn tortillas on the grill for about 30 seconds on each side until pliable.
To assemble the tacos, place a few slices of grilled steak on each tortilla, top with grilled corn, drizzle with the creamy sauce, and sprinkle with queso fresco and cilantro. Add avocado slices if desired.
Serve immediately and enjoy!