1. In a small pan, gently bring sugar and vinegar to the boil; simmer for 5 minutes, then reserve. Wash peppers, cut into wedges, remove seeds and white pulp, then peel. Dice into ~1 cm pieces.
2. Finely dice onion and gently fry in extra virgin olive oil until translucent. Add peppers, season, cover and cook, stirring regularly and adding a little water to keep the mixture wet. When done, peppers should be soft. Blend some of the peppers with an immersion blender, leaving about half intact. Add basil, cover.
3. Meanwhile, cook the pasta al dente in a large pot of salted water.
4. Drain the pasta and transfer to a pan with peppers. Emulsify with a little pasta water and extra virgin olive oil. Add a little vinegar reduction, one teaspoon at a time, until the right sourness is achieved.
5. Season, add chopped parsley and stir well. Spoon a little sauce on the plate. Top with the pasta and some extra sauce and peppers. Finally, if desired, top with fresh parsley leaves and a generous amount of extra virgin olive oil.