Heat the oil in a large frying pan over a medium heat.
Add the red onion and yellow pepper and fry gently for 8 minutes to soften without colouring.
In the meantime, put the pasta on to cook following the instructions on the packet.
Add the tomatoes, olives and basil leaves to the frying pan. Mix well and simmer for about 5 minutes.
Drain the pasta when it is cooked.
Add the mascarpone into the mixture in the frying pan, stirring for a minute or two to combine.
Season with black pepper and stir in the drained pasta.
Serve with grated cheese and extra basil to garnish (optional).