Heat the olive oil and butter in the base of a tagine over a medium heat, stir in the garlic and cook for 1–2 minutes until it begins to colour. Place the fish in the tagine and cook for approximately 2 minutes on each side until lightly brown.
Remove the tagine from the heat, scatter a little salt over the fish and arrange the slices of tomato and lime over the top of the fish.
Cover and place in a preheated oven, 180°C (350°F), Gas Mark 4, for about 15 minutes. Remove the lid and bake for a further 5 minutes until the fish is cooked through. Scatter the parsley over the top and serve with wedges of lemon to squeeze over the fish.