In a large frying pan saute' the julienned onions in the olive oil on medium to medium high heat 1 minute.Add the snapper and cook 2 minutes or until slightly browned. Turn and brown the other side 2 minutes.
Add the wine,tomatoesand half of the pepper flakes. Slice the olives in half and add to the skillet.Season with salt to taste and simmer 10 minutes basting the fish as it cooks.
Chop the parsley and add it. Squeezing the halfed lemon over the fish and simmer 1 minute, spoon sauce over the red snapper and serve.