In a large, deep-sided skillet add the onion and carrots and saute over medium heat until softened, around 10-12 minutes. (more if the pieces are larger)
Add in the garlic and saute for one minute. Stir in the tomatoes, salt, basil, red pepper flakes and sugar.
Simmer on low heat for 30-35 minutes, or until the sauce has thickened and the oil is floating on top and is orange colored.
Stir and taste test. Add more sugar and salt/pepper if needed.
Sprinkle with the fresh parsley when serving.
Notes
Adjust the sugar to taste, this will depend on how acidic the tomatoes are to start
This can be put into freezer safe bags and frozen flat for up to 6 months. Just defrost and use.