Preheat the oven: Set to 425°F (220°C).
Line two sheet pans with parchment for easy cleanup.
Prep the veggies: Toss broccoli, peppers, and red onion with 1 tablespoon oil, a pinch of salt, and a light sprinkle of Cajun seasoning. Spread evenly on one sheet pan.
Start roasting: Roast the vegetables for 10 minutes to give them a head start.
Season the salmon: Pat fillets dry. Mix Cajun seasoning, garlic powder, paprika, a pinch of salt (if needed), and a few grinds of pepper.
Rub salmon with 1 teaspoon oil and coat evenly with the spice mix.
Add salmon to the oven: Slide the veggies to the top rack. Place salmon on the second sheet pan and bake both pans for 8–12 minutes, depending on thickness. You’re aiming for opaque edges and slightly translucent centers.
Finish under the broiler (optional): For lightly charred edges, broil salmon for 1–2 minutes at the end.
Keep a close eye to avoid burning.
Prepare your base: While the pans roast, steam cauliflower rice or reheat cooked brown rice/quinoa. Season lightly with salt, pepper, and a squeeze of lemon.
Add brightness: When the salmon comes out, drizzle with 1 tablespoon lemon juice. Toss roasted veggies with cherry tomatoes if using for a juicy pop.
Assemble meal prep boxes: Divide the base among 4 containers, top with a salmon fillet, and add a generous scoop of veggies.
Garnish with fresh herbs and tuck in lemon or lime wedges.
Cool, then store: Let everything cool for 15–20 minutes before sealing to prevent condensation and soggy textures.