In a large bowl combine; eggplant, onions, red pepper and the 1/4 cup salt. Mix together cover and let stand over night in refrigerator.
Day two:
Rinse, drain well and put into a large pot then add mustard, garlic, cumin, vinegar, brown sugar, pepper flakes, 1/2 T. salt, pepper, tomatoes and tomato paste. Bring to a boil and simmer for 15 minutes.
Ladle into sterilized jars filling to 1/2" headspace. I added 1 T. bottled lemon juice to each of the pint jars and 1/2 T to half pint. Remove air bubbles, Wipe rims, add hot lids and rings. Water bath jars for 15 minutes at a full boil.