In a bowl, combine olive oil, minced garlic, lime juice, lime zest, ground cumin, chili powder, salt, and pepper. Add the flank steak and coat evenly. Cover and let marinate in the refrigerator for at least 30 minutes (or up to 2 hours for maximum flavor).
Heat a grill pan or skillet over medium-high heat. Remove the steak from the marinade, letting the excess drip off. Grill the steak for about 4-5 minutes on each side, or until it reaches your preferred doneness (medium rare is about 135°F).
Transfer the cooked steak to a cutting board and let it rest for about 5-10 minutes. This allows the juices to redistribute.
While the steak is resting, prepare the base. In bowls, add a generous scoop of cooked brown rice or quinoa.
After resting, slice the steak against the grain into thin strips.
Top the rice or quinoa with sliced steak, cherry tomatoes, sliced avocado, corn, and black beans. Sprinkle with chopped cilantro for freshness.
Serve the bowls warm, with optional lime wedges on the side for an extra burst of flavor.
Notes
For maximum flavor, marinate the steak for up to 2 hours.