Marinate the Steak: In a bowl, whisk together lime juice, olive oil, cilantro, minced garlic, cumin, chili powder, salt, and black pepper. Add the flank steak, coating it well. Cover and refrigerate for 30 minutes, or up to 4 hours for deeper flavor.

Prepare Rice and Beans: Cook rice according to package instructions until fluffy. In a saucepan, heat the black beans on medium, adding seasoning if desired. If using fresh corn, cook it during this time as well.

Cook the Steak: Preheat the grill to medium-high. Remove the steak from the marinade and grill for about 4-5 minutes on each side for medium-rare (130°F). Once cooked, let the steak rest for 5-10 minutes, then slice it against the grain.

Assemble Bowls: Start by dividing the cooked rice among serving bowls. Layer on black beans, corn, halved cherry tomatoes, sliced avocado, and diced red onion. Add the sliced steak on top, sprinkle with feta if using, and garnish with extra cilantro and lime wedges.