In a saucepan over medium heat, brown the shallot in 15 ml (1 tablespoon) oil. Season with salt and pepper. Add the pineapple and continue cooking for 4 to 5 minutes. Deglaze with the vinegar. Transfer to a blender, add 60 ml (1/4 cup) oil and purée until smooth. Adjust the seasoning. Pour into a small saucepan and set aside over low heat.
Fill a large saucepan with water and heat until it starts to simmer.
Season the fish with salt and pepper. Place each piece in a bag. Seal partially and squeeze out as much air as possible. Seal tightly.
Place the bags in the water and cook over low heat for about 12 minutes.
Serve the fish with the pineapple sauce.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.