In a medium bowl, combine fresh lime juice, olive oil, chopped cilantro, minced garlic, ground cumin, chili powder, salt, and black pepper. Add the flank steak, ensuring it is fully coated with the marinade. Cover and refrigerate for at least 30 minutes.

While the steak marinates, cook the rice according to package instructions. In a small saucepan, heat the black beans over medium heat for about 5 minutes until warmed through. Set both aside.

Prepare the corn by bringing a pot of water to a boil. Cook the corn for about 3–4 minutes until tender. Drain and set aside.

Preheat a grill to medium-high heat. Remove the steak from the marinade and grill for approximately 4-5 minutes per side for medium-rare. Let it rest for 5–10 minutes before slicing.

Divide the cooked rice among bowls and top with black beans, corn, cherry tomatoes, avocado, and sliced steak. Sprinkle with red onion and feta cheese if desired. Garnish with cilantro and lime wedges.