In a small bowl, mix together chili powder, cumin, garlic powder, onion powder, lime juice, olive oil, salt, and pepper to create a marinade.
Place the flank steak in a shallow dish and pour the marinade over it, ensuring the steak is well coated. Cover and marinate for at least 30 minutes, or up to 2 hours for more flavor.
Preheat your grill or stovetop grill pan over medium-high heat. Once hot, remove the steak from the marinade and add it to the grill. Cook for about 4-5 minutes per side for medium-rare, or until desired doneness is reached.
Remove the steak from the grill and let it rest for 5 minutes before slicing it thinly against the grain.
In a large serving bowl, combine the mixed salad greens, cherry tomatoes, avocado, and red onion. Toss gently to mix.
Arrange the sliced steak on top of the salad and drizzle any leftover marinade over if desired.
Garnish with fresh cilantro before serving.
Notes
Serve the salad in a large bowl with steak slices arranged beautifully on top. Add a lime wedge on the side for extra visual appeal.