You could try soaking the onion in ice water for about 10 min before adding it to the salsa. This will "tame" the taste a bit. I use this method when using strong onion in salads to cut the taste a bit. Hope it helps!
By
06/11/2009
The only thing I can think of is to add more chopped tomato, pepper and whatever else is in the salsa, (maybe throw in some corn and/or olives too) to lower the proportion of onion in the whole.