Prep the oven and pan: Preheat the oven to 400°F (205°C). Line a large baking dish or sheet pan with parchment for easier clean-up.
Trim and pat dry: Trim excess fat from the chicken. Pat dry with paper towels so the spices stick and the chicken browns better.
Season the chicken: In a bowl, mix olive oil, garlic powder, onion powder, cumin, smoked paprika, chili powder, salt, and pepper.
Rub the mixture evenly over the chicken breasts.
Add the salsa: Place the chicken in the baking dish. Pour 1 cup of the salsa over the top, coating each breast. Reserve the remaining 1/2 cup for after cooking.
Bake: Bake for 18–22 minutes, or until the thickest part reaches 165°F (74°C).
Cooking time may vary with thickness. Avoid overcooking.
Rest and shred or slice: Let the chicken rest 5 minutes. Either slice it crosswise or use two forks to shred right in the pan with the salsa juices.
Add beans and corn: Stir in black beans and corn to the pan.
The residual heat will warm them through. If needed, return to the oven for 3–5 minutes.
Finish with fresh salsa: Spoon the reserved 1/2 cup salsa over the chicken mixture for a bright, fresh pop.
Build the meal prep boxes: Divide rice or quinoa into 4–5 containers (about 1/2 cup each if using). Top with equal portions of salsa chicken, beans, and corn.
Garnish and cool: Add cilantro and a squeeze of lime.
Let containers cool, uncovered, for 15–20 minutes before sealing and refrigerating.