Peeling tomatoes: Drop tomatoes into a pot of boiling water for 1-2 minutes. Take them out of the pot and immediately drop into ice water. After they're cooled a bit you will be able to peel the skin off with the help of a paring knife.
Place chopped tomatoes in a colander, sprinkle with salt, and let drain for 30 minutes.
Heat oil in a medium sauté pan. Sauté onion in oil for 5 minutes. Add garlic and red pepper flake for last minute. Add tomatoes, basil, salt, pepper and sugar. Allow to simmer slowly for 30 minutes. Add parsley at the end. Adjust seasonings to your taste.