Heat butter and olive oil over medium heat.
Add onions, carrots, celery, and garlic and saute for a couple minutes.
Pour in tomato sauce and add salt, pepper, and sugar to taste.
Stir and cook over low heat for 25 minutes, stirring occasionally.
While sauce is cooking, cook pasta according to package directions.
Drain pasta reserving 1 cup pasta water.
At end of 25 minutes, remove sauce from heat and stir in cream.
Add parmesan and check seasonings.
Stir in pasta and chopped basil and serve immediately (thin with pasta water before adding basil if needed).