Preheat the oven to 450°F. Lightly grease a large baking sheet with olive oil or nonstick cooking spray. Set aside.
In a large bowl, add the bell peppers, onion, 1 tablespoon olive oil, chili powder, kosher salt, onion powder, garlic powder, ground cumin, smoked paprika, and black pepper. Toss together until everything is combined and evenly coated.
Coat the flank steak on both sides with the remaining 1 tablespoon of olive oil, then season generously with kosher salt and black pepper on both sides.
Transfer the flank steak to the center of the prepared baking sheet and spread out the peppers and onions around it in an even layer.
Place in the oven and bake for 10-12 minutes for a thinner flank steak, or 15 minutes for thicker flank steak.
Remove from the oven and move the rack to the top position right under the broiler.
Transfer the veggies to a bowl and cover them with a plate to keep them warm. They should be tender and fully cooked through.
Place the baking sheet with the steak on the top rack. Broil for 2-5 minutes depending on the thickness.
Transfer the steak to a large cutting board and let it rest for 5 minutes. Slice it into thin strips and then add back to the baking sheet along with the peppers and onions.
Top everything with lime juice and cilantro, and serve immediately in warm corn tortillas, flour tortillas, Mexican rice, or cilantro lime cauliflower rice.
To make sure the steak is cooked to your preferred temperature, I recommend buying an oven-safe meat thermometer like this one so you can keep an eye on the temperature as the steak is in the oven.
To keep the strips of steak from being too chewy, make sure you slice it against the grain and as thinly as you can.