Mix the salt with the sliced tomatoes and allow to stand overnight. Drain.
Ina large pot combine vinegar, sugar, mustard seeds, celery seeds, turmric and onions. Bring to a boil and simmer about 5 mins.
Stir in the drained tomatoes, onions and the peppers.
Bring to a boil and simmer gently 20 mins or so.
I usually simmer a little longer as I like it quite soft.
Pack into hot sterilized jars and seal