Soak the cashews overnight in room temperature water or leave them soaking for 20 minutes in boiling hot water.
Boil water in a big pot and add the pasta. Cook following packet instructions. Drain, rinse and leave aside. Save some of the pasta water for later.
Finely chop the onion and add it to a preheated pot with some olive oil. Stir fry for a couple of minutes until it starts to soften and add finely chopped garlic. Keep cooking for 2-3 minutes.
Add the chopped tomatoes, fresh or dried herbs, sugar, salt and pepper. If you are using fresh tomatoes you can blend them before adding them into the pot. Stir until everything is combined and leave simmering for 30-40 minutes stirring occasionally. Keep tasting the sauce and adjust to taste.
Drain and rinse the cashews. Add them in a blender together with the yeast flakes and water or stock.
Blend until you have a smooth consistency.
Mix the creamy sauce with the tomato sauce and combine well. Add the cooked pasta and if needed, some of the pasta water.
Before serving, add some fresh basil and sun-dried tomatoes, finely chopped.