In a large pot, mix the onion, tomatoes, green bell peppers, red bell pepper, Anaheim chile peppers, banana peppers, and jalapeno peppers. Stir in the tomato sauce, tomato paste, vinegar, diced tomatoes, and SPLENDA(R) Brown Sugar Blend. Season with chili powder, Italian seasoning, and salt. Bring to a boil, reduce heat to low, and simmer 1 hour.
Mix the cornstarch and water, and stir into the salsa to thicken. Transfer salsa to sterilized jars, leaving 1/2 inch headroom, and seal. Process jars in a boiling water bath 15 minutes. Store unsealed jars in the refrigerator.