Pre heat oven to 180℃ fan/200℃/Gas Mark 6.
Finely chop or grate the courgettes.
Heat the oil in a large pan and cook the onion and garlic for 5 minutes until starting to soften.
Add the courgettes and cook for 10 minutes until they are starting to colour and no longer look wet.
Add the passata, oregano, balsamic, pesto, tomato puree and plenty of salt and pepper, and cook for another 10 minutes until you have a thick sauce.
Layer the mixture first in a lasagne dish, followed by the lasagne sheets, then the ricotta, mozzarella and more salt and pepper. Repeat again, and finish with a layer of cheese on top.
Bake for 30 minutes or until crispy and golden.