The taste of late summer, to me, is that of very fresh tomatoes from the farm, tomatoes that never saw the inside of a refrigerator or rode on a tractor-trailer across state lines.

If you can't make this with farmer's market fresh tomatoes, don't use supermarket tomatoes! Canned tomatoes were at peak freshness when they went into the can, but supermarket tomatoes are bred for shippability and picked unripe, then artificially "ripened" in the truck with ethylene gas. Of course, artificial ripening is artificial, away from the sun, and it's the sunshine that the plant uses to make the fruit sweet.