Peel the onion and chop finely. Cut the pepper in half, deseed, remove the white veins, wash, dry and cut into strips. Clean and wash thoroughly the lettuce in plenty of cold water, drain and dry and cut into strips. Heat up some oil in a saucepan and sauté the onion until soft, but not golden; add the pepper and brown for a few minutes, stirring with a wooden spoon; add the wine to the mixture and let it evaporate over high heat; season with salt and pepper, cover with a lid, and cook for 15 minutes. A minute from the end, mix in the lettuce and let it flavor. In the meantime, cook the pasta in plenty of boiling salted water and drain when al dente. Put in a serving dish, stir in the sauce and serve warm.