With the rack in the middle position, preheat the oven to 425°F (220°C).
On a non-stick or parchment paper-lined baking sheet, combine the cabbage and oil. Season with salt and pepper. Bake for 10 minutes or until the cabbage is slightly golden.
Meanwhile, in a shallow bowl, combine the spices and salt. Coat the top of the salmon pieces with the spice mix.
Nestle the fish in the cabbage, making sure that the salmon skin is in direct contact with the baking sheet. Bake for 10 minutes or until the desired doneness.
Meanwhile, in a pot, bring the broth and milk to a boil. Season generously with salt and pepper. Slowly add the polenta and garlic powder. Cook for 5 minutes, stirring constantly with a wooden spoon. Add the butter. Adjust the seasoning. Serve immediately with the salmon and cabbage.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.