Boil pasta in plenty of salted water. In the meantime, cook the onion with 20 gr of butter and a teaspoon of sugar, adding water until the onion is cooked. Then, blend the onion with cream and add salt if necessary.
In a large pan, stir-fry the smoked bacon with a pinch of butter, add the onion cream and sauté the pasta "al dente" with them.
Serve the spaghetti with smoked bacon and add lots of pepper.