Place the flour and salt on a wooden board, create a small nest in the centre, and gently pour the warm water in. Gradually mix the flour and water together, bringing the ingredients together into a firm dough. Knead the pasta until smooth, for 5 minutes. Rest for an hour.
Heat the olive oil in a pan over medium heat and add the onions. Cook until golden brown. Add the guanciale strips and fry for a few more minutes. Pour in the white wine and gently cook until the liquid has evaporated. Add the chopped tomatoes, lower the heat and cook for an hour or until the sauce thickens slightly.
Roll out the dough to 8mm thick. Cut the pasta dough into strips, approximately 8mm wide. Take a strip and pinch it so that long edges roughly join together. Make sure there is no flour on the table, then use your hands to roll the dough into a cylindrical shape. Start from the center and roll out rapidly until you reach the end. Repeat with the remaining strips of pasta dough.
Add salt to a pot of water and bring to a boil. Cook the pici for six minutes, drain and add to a pan over low heat with the sauce. Quickly cook for a minute to allow everything to combine together. Enjoy!