Pre-heat oven to 450 degrees F.
In heavy Dutch oven, place tomatoes, onion and garlic.
Add olive oil and stir.
Season with salt, pepper and red pepper flakes to taste.
Place in oven and roast for 45 minutes to 1 ½ hours (check and stir when you begin to smell the sauce, then keep roasting until you like the look and feel).
When sauce reaches desired consistency, remove from oven.
Lightly mash tomato mixture with heavy spoon or potato masher, then add basil and stir.
Serve over pasta, to top fish or chicken, or as side dish.
Sauce flavor deepens deliciously over 1 to 3 days while refrigerated.
Can also be frozen.
