Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Slice the red and yellow bell peppers into thin strips and the zucchini into half-moons.
Place the vegetables on the baking sheet, drizzle with half of the olive oil, and sprinkle with sea salt and black pepper.
Toss the vegetables to coat evenly and roast in the oven for 15 to 18 minutes until tender and slightly charred at the edges.
While the vegetables roast, pat the salmon fillet dry with a paper towel and rub the remaining olive oil over all sides.
Evenly coat the flesh side of the salmon with the Cajun seasoning, pressing it gently into the fish.
Heat a non-stick or cast-iron skillet over medium-high heat. Once hot, place the salmon in the pan, skin-side up first.
Sear the salmon for 4 to 5 minutes per side, or until the internal temperature reaches 145°F and the spice crust is golden.
Plate the roasted vegetables and top with the Cajun salmon fillet.
Finish the dish with a generous squeeze of fresh lemon juice over the fish and vegetables before serving.