Lightly brush the whole aubergine with oil, and place on a baking tray. Roast for around 25 minutes at 190°C (Gas Mark 5 / 375°F). Turn the aubergine over, and add the chunks of red pepper and the cherry tomatoes, also lightly tossed in oil. Roast for a further 25 minutes, until all the vegetables are soft and juicy. The aubergine should be very soft.
Cut the aubergine in half, and set aside until cool enough to handle. Scrape the flesh from the middle of the aubergine - it should pull away easily from the skin. Add the aubergine flesh to a food processor, along with the roasted peppers and tomatoes, garlic, tahini, cashews, smoked paprika, and a couple of sprigs of basil. Season generously, and blend thoroughly.
Boil the pasta in plenty of water until cooked al dente, then drain, and add the roasted red pepper sauce. Mix well over a low heat for a minute or two, until piping hot. You can add a dash of water if the sauce seems too thick. Serve with fresh basil and some extra chopped cashew nuts, if desired.