Add a little oil to a sauté pan and place over a medium heat.
Add the n’duja and let it melt into the oil.
Add, the chilli flakes and tomato purée and cook everything, stirring, for about 3-4 minutes to really caramelise the tomato purée.
Turn the heat down on your pan and finely slice your onion and garlic.
Add the onion and garlic to the pan and stir through, allowing everything to soften, for about 5 minutes.
Slice the cherry tomatoes and add to the pot.
Slice the red chilli and add to the pot as well.
Cook for a few minutes to allow the cherry tomatoes to begin to break down.
Add the pasta and 600ml (2 1/4 cups) of boiling water.
Stir the pasta occasionally, to make sure it doesn’t stick to the pan and allow the pasta to soak up all the liquid - cooking until the pasta is al dente and adding more hot water if you feel the pasta is getting a little dry.
Add the butter and spinach to the pot and stir to wilt the spinach.
Serve the pasta in bowls, topped with torn mozzarella, a few basil leaves, a good glug of extra virgin olive oil and some salt and pepper.