Heat the oven to 200°C (Gas Mark 6 / 400°F).
Place the cauliflower slices on a lined baking tray, and drizzle with oil. Season with salt and pepper, and place in the oven for around 20 minutes, until fairly soft and slightly crispy around the edges.
Add a couple of slices of tomato to each piece of cauliflower, and then add the grated cheese. Return to the oven for 5 more minutes until the cheese has melted and is slightly crispy.
Serve topped with fresh basil if desired.