Peel the onion, sweet potato and beetroot and slice them into thin rings.
Place them into a baking dish previously drizzled with olive oil.
Peel the onion, sweet potato and beetroot and slice them into thin rings. Place them into a baking dish previously drizzled with olive oil. Salt the beetroot and the sweet potato. Place the beetroot onto the onion, then the sweet potato onto the beetroot. Drizzle with some olive oil and season with thyme leaves. Top it all with unpeeled garlic. Take the fish out of the packaging.
Score the fish in two places on one side. Season with salt and pepper and drizzle with olive oil. Preheat the oven to 180°C. First put the vegetables in to bake for approximately 10 minutes, then place the fish on top and continue baking at 200°C until the fish becomes golden in colour. Not longer than 20 minutes. Serve with salad.