Holding calamari tube, pull off head and tentacles; set aside. Rinse squid tubes under cold water, rubbing off purplish skin. Pull out and discard "pen" (long clear plastic-like skeleton) from centre of tubes.
On cutting board, pull off and discard fins from tubes. Cut off and discard eyes and head from tentacles, keeping tentacles attached on ring on top. Squeeze hard beak from centre of tentacles and discard.
Cut tubes crosswise into 1/2" wide rings; pat dry.
In saucepan, heat oil over medium heat; cook onion and garlic, stirring occasionally, until softened, about 3 minutes. Add wine and hot pepper flakes; cook for 1 minutes.
Add tomatoes; bring to a boil. Reduce heat and simmer for 5 minutes.
Add squid; simmer until tender, about 3 - 5 minutes. Sprinkle with salt.
Note: fresh tomatoes could be used.but the sauce would need to cook down probably 10 minutes more.