Start by preheating your oven to a high broil or grill setting. Lightly grease a large sheet pan to prevent sticking. A hot oven helps create beautifully roasted vegetables and flaky salmon.
In a bowl, whisk together lime juice, parsley, olive oil, water, garlic, chilli flakes, cumin, salt, and honey. Mix until well combined. This marinade will flavor both the salmon and vegetables.
Place the salmon fillets, bell peppers, and onion wedges on the sheet pan in a single layer. Pour half of the marinade over everything and gently toss the vegetables. Turn the salmon to coat evenly.
Place the pan in the oven and broil until the peppers begin to char and the salmon starts to turn opaque. This usually takes around 8–10 minutes depending on thickness.
Brush the remaining marinade over the salmon and vegetables. Return the pan to the oven and broil for another 30–60 seconds to achieve a glossy, caramelized finish.
Remove from the oven and plate the salmon with vegetables. Spoon any remaining juices over the top and finish with extra lime juice if desired.