1. Chop the courgettes, aubergines, red onions, peppers and tomatoes to roughly the same size and thickness. Pick the basil leaves and set aside.
2. Heat two tablespoons of olive oil in a pot over a medium heat; add the onions and garlic and cook for 10-15 minutes until softened and golden.
3. Add the tinned tomatoes and tomato passata, the balsamic vinegar and a good pinch of sea salt and black pepper.
4. Mix well, breaking up the tomatoes with the back of a spoon. Cover the pan and simmer over a low heat for 30-35 minutes, or until reduced, sticky and sweet. Tear in the basil leaves, finely grate in the lemon zest and adjust the seasoning, if needed.
5. Preheat the oven to 180°C/160°C fan/gas mark 4
6. To assemble, spread a layer of the tomato sauce into a baking dish and top with an even layer of the vegetables. Repeat until all of the sauce and vegetables have been used up, finishing with a vegetable layer.
7. Drizzle with olive oil and bake for 30 minutes until the vegetables are tender. Garnish with fresh basil leaves and a final drizzle of olive oil if needed.
8. Serve with a hunk of bread or steamed rice.