Whisk together lime juice, olive oil, chopped cilantro, minced garlic, cumin, chili powder, salt, and black pepper in a medium bowl until well combined.

Place flank steak in a resealable bag or shallow dish. Pour marinade over the steak and coat well. Seal or cover and refrigerate for at least 30 minutes, or 2 to 4 hours for maximum flavor.

Cook rice according to package directions if not already prepared. Warm black beans in a small saucepan over medium heat for about 5 minutes. Heat corn if using frozen or canned.

Preheat grill or grill pan over medium-high heat and oil it to prevent sticking.

Remove steak from marinade, letting excess drip off. Discard the marinade. Grill steak for 4 to 5 minutes per side for medium-rare (internal temperature 130°F). For medium, cook to 140°F. For medium-well, aim for 150°F. Adjust time for preferred doneness.

Let steak rest 5 to 10 minutes after cooking. Slice thinly against the grain (perpendicular to the lines running through the meat) for maximum tenderness.

Spoon rice into bowls (1/2 to 1 cup per serving). Top with black beans, corn, and cherry tomatoes. Lay strips of sliced steak on top.

Add avocado slices, red onion, feta cheese (if using), and extra cilantro. Finish with lime wedges for squeezing over the bowl.