Position a rack in the center of the oven and heat the oven to 375°F.
In a blender, combine the red pepper, vinegar, and honey. Turn the blender on, let it run for a few seconds, and then drop the garlic through the feed hole. With the blender still running, slowly pour in the 1/4 cup oil and process until the mixture is smooth, about 1 minute, stopping to scrape down the lid and sides of the blender jar as necessary. Season with salt and pepper to taste.
Set the fish skin side down on a plate and season with salt and pepper. Heat the remaining 2 Tbs. oil in a large ovenproof skillet (preferably cast iron) over medium-high heat until shimmering. Put the fish skin side up in the skillet, and cook until well browned, 3 to 5 minutes. Flip the fish, turn off the heat, and transfer the pan to the oven. Roast until the fish is flaky, moist, and cooked through (use the tip of a paring knife to check), 5 to 7 minutes.
Transfer the fish to dinner plates, spoon about 1 Tbs. purée onto or around each piece, sprinkle with the chives or marjoram, and serve immediately with the remaining purée on the side.
Any leftover purée will keep, refrigerated, for up to 5 days. You can serve it with chicken or pork, or thin the purée with additional olive oil to make a dressing for steamed, sautéed, or roasted asparagus or a salad of romaine hearts, red onion, and hard-boiled egg.