Peel the onion and chop it finely. Cut the pepper in half, deseed it and remove the white veins, wash it and dry it, then slice it into strips. Clean and wash accurately the lettuce in plenty of cold water; drain it and dry it delicately in a tea towel then cut it into strips.In a saucepan heat some oil, add the onion and fry until soft but not golden; add the pepper and brown it for a few minutes, stirring with a wooden spoon. Add the white wine to the sauce and let it evaporate over a high heat.Season with salt and pepper and simmer, covered for 15 minutes. A minute before it is ready, add the lettuce and mix well to blend all the flavours.In the meanwhile, cook the pasta in plenty of boiling salted water and drain it al dente. Place it in a serving dish, add the sauce and serve immediately warm.