Cook pasta according to package directions but add 1 tablespoon cooking oil to the water before adding the pasta. Drain and set aside. Reserve approximately 1 cup of the pasta cooking water.
In a large skillet, add two tablespoon cooking oil over medium high heat.
When the oil is heated, add onions and cook for 10 minutes or until soft.
Add garlic and cook for two additional minutes.
Stir in sugar, pepper flakes, and salt
Pour in tomatoes and stir.
Reduce heat to medium, cover and cook for 30 minutes. Stir occasionally and mash some of the tomatoes with the back of a wooden spoon as they soften.
Add cooked pasta to the skillet. Starting with 1/4 cup of the pasta water, add as much as you need to make the pasta and sauce smooth. Toss pasta and sauce with tongs until mixed.
Serve with additional grated Parmesan cheese.