Preheat and prep. Heat your oven to 425°F (220°C). Line a large sheet pan with parchment for easy cleanup.
Pat the chicken dry with paper towels.
Mix the spice blend. In a small bowl, combine chili powder, cumin, smoked paprika, garlic powder, onion powder, oregano, salt, pepper, and cayenne if using.
Season the chicken. Toss the chicken with 1 tablespoon olive oil and about two-thirds of the spice blend. Add half the lime zest and a squeeze of lime juice. Let it sit while you prep the veggies.
Season the veggies. On the sheet pan, toss sliced peppers and red onion with 1 tablespoon olive oil, the remaining spice blend, and the rest of the lime zest.
Arrange and bake. Push the veggies to the sides and place the chicken in the center.
Bake for 16–22 minutes, depending on thickness, until the chicken reaches an internal temp of 165°F (74°C) and the peppers are tender with a little char.
Rest and slice. Transfer chicken to a cutting board and rest 5 minutes. Slice thinly against the grain or dice into bite-size pieces. Toss the sliced chicken with any pan juices for extra flavor.
Warm tortillas or prep grains. If using tortillas, warm them in a dry skillet for 30–45 seconds per side or microwave wrapped in a damp towel.
If using bowls, fluff cooked brown rice or quinoa with a fork.
Assemble for meal prep. Divide rice or quinoa among 4–6 airtight containers. Top with black beans, peppers and onions, and sliced chicken. Add shredded lettuce or cabbage, keeping it separate if possible.
Pack salsa, Greek yogurt, and avocado on the side.
Finish with fresh touches. Right before eating, add a squeeze of lime, a spoon of salsa, a dollop of Greek yogurt, and chopped cilantro. If using tortillas, build tacos fresh to keep them from getting soggy.