In a large, non-stick saucepan, sauté the onion in a small amount of water until it begins to brown, about 5-8 minutes. Add the garlic, paprika, and red pepper (optional), and stir for one minute. Add the salt, eggplant, peppers, vegetable broth, and tomatoes. Add liquid smoke if desired. Cover and simmer until the eggplant is tender, about 15-20 minutes.