To caramelise the onion: butter, 2 spoonful of white vinegar, 1 teaspoon of caster sugar
To make your pasta dough, make a well with the flour on a wooden board, then crack the eggs into the flour and mix with a fork. Once it is not too wet, start kneading with the hands until smooth. The dough must be soft and elastic but not too wet, so keep adding flour if needed. Try and make it into a ball, then wrap it in cling film and put in the fridge for half an hour so that it can rest.