Heat the oil in a large pan over a medium heat. Add the onions and fry gently until softened.
Add the red pepper and fry for 4-5 minutes to soften.
Add the tomatoes, bring to a simmer and continue to heat gently for 20-30 minutes.
Tear up the parsley and add it to the tomato mix. Season well with salt and freshly ground black pepper.
Add the cooked spaghetti to the tomato sauce and mix well.
Serve onto warm plates and drizzle liberally with truffle oil.
Type the ingredients you want to use, then click Go. For better results you can use quotation marks around phrases (e.g. "chicken breast"). Alternatively you can search by chef, programme, cuisine, diet, or dish (e.g. Lasagne).