Using scissors, remove the fat from the bacon and cut into small pieces. Cook the bacon over a low heat until it is no longer translucent. Do not allow it to brown.
Add the tomatoes, sugar and ½ a teaspoon of salt. Simmer gently.
Put the pasta on to cook, grate the cheese and dice the butter.
When the pasta is nearly ready, mix the cornflour with 1 table spoon of water and stir into the sauce. Cook for a further two minutes then remove from the heat.
When the pasta is cooked, drain reserving a little of the pasta water. Return the pasta to the pan. Tip the cheese and butter onto the pasta then add the thickened sauce. Stir together adding some reserved pasta water to loosen if necessary.