Preheat your oven to 200C/400F/Gas mark 6 and lightly grease a large ovenproof dish, then place to one side.
In a medium-sized mixing bowl add in the pasta, tinned tomatoes, cherry tomatoes, sliced onion, passata, water, herbs, seasoning and baby spinach leaves and gently mix everything together.
Pour half of this mix into your ovenproof dish.
Sprinkle half of your sliced mozzarella over the mix then cover with the remaining pasta mixture.
Sprinkle the remaining mozzarella and the cheddar over the top and cover with tin foil.
Pop this into your hot oven for 30 minutes.
After this time remove the foil and continue cooking for a further 10 - 15 minutes. You are looking for the cheese to start to turn golden and most of the liquid to have been absorbed by the pasta.
Take your dish out of the oven and serve.
Any left-overs can be stored in the fridge once cool and must be eaten within 3 days. Reheat in a microwave for a few minutes or enjoy cold.