Cook the pasta following the instructions on the packet. Once cooked, drain the water but leave the pasta in the saucepan. In a frying pan heat the oil and add the chopped onions, cooking them until they are beginning to brown. When this happens, bung in the chopped tomatoes, tuna, sugar (and herbs if you like) and combine. After a couple more minutes add this mixture to the saucepan of cooked pasta and stir to coat the pasta. Finally, pour the saucepan of pasta and sauce onto the plate of your choice. Ta-da!