Preheat your oven to 475°.
Toss the bell peppers, the onion, and the garlic with the olive oil.
Lay two sheets of foil, each large enough to wrap a fillet with some room for steam space, on a clean counter.
Spray the sheets with cooking spray.
Lay down the bluefish fillets. Season with salt. Rub it in. Gently. With your fingers.
Lay an even blanket of the bell pepper mixture on each fish fillet. Use a rubber spatula to scrape every last drop of olive oil onto the fillets.
Lay down some basil over the peppers.
Decoratively layer the lemons on the fillet.
Wrap the foil packets.
Place the packets on a roasting pan and bake for 18 minutes or until the fish flakes easily with a fork, depending upon the thickness of the fish. A safe bet is to simply allow the fish to rest after taking it out of the oven for an additional 5 minutes or so, both to allow the steam to subside a bit and to ensure that the fish and vegetables are cooked through.