Whisk together olive oil, lime juice, cumin, garlic powder, salt, and pepper in a small bowl.
Coat the steak thoroughly with the marinade and allow it to sit at room temperature for 10 minutes.
Heat a cast-iron skillet over medium-high heat until wisps of smoke appear.
Sear the steak for approximately 4-5 minutes per side for medium-rare, or until internal temperature reaches 135°F (57°C).
Transfer the steak to a cutting board and let rest for at least 5 minutes.
In the same skillet, briefly toss the corn kernels for 2 minutes until lightly charred.
Slice the rested steak against the grain into 1/4-inch thick strips.
Divide the cooked rice into four serving bowls.
Top each bowl with equal portions of steak, black beans, charred corn, red onion, and avocado slices.
Garnish with chopped cilantro and serve immediately with lime wedges.