Pre heat oven to 220c/200c fan Place the capsicums, eggplant and onion in a bowl, add 2 tablespoons of the olive oil and season with sea salt and ground black pepper. Toss everything together well then scatter into a shallow baking dish and bake for 25 minutes.
Remove the dish from the oven, turn the vegetables, then cook for a further 5–10 minutes, or until well softened and lightly browned.
Remove the dish from the oven, stir in the garlic, basil and tomatoes, arrange the halloumi on top, drizzle with the remaining oil, season with more ground black pepper and return to the oven for a further 15 minutes, or until the halloumi is hot and lightly browned.
Scatter with more fresh basil to serve