Preheat oven at 400 degrees Fahrenheit (200 degrees Celsius).
Wash the eggplant. Remove most of the stem. Peel parts of the eggplant lengthwise all around so that you have a striped eggplant. Make 3 deep slits lengthwise about an inch apart.
Place eggplant in a pan, drizzle with a bit of olive oil and sprinkle with salt and pepper and roast for about 1 hour.
In the meantime start on the onion mixture. Sauté the chopped onion in a pan with 1/3 cup olive oil until soft. Add the chopped garlic, tomato, parsley and sugar and ½ cup water and simmer for about 15-20 minutes minutes. Add additional water if needed. When the mixture is ready it should not be watery.
Once the eggplant is ready, open one of slits and stuff with the onion mixture. Do this with all the eggplant and place in the pan. Drizzle with olive oil. Sprinkle with feta. Add a bit of water at the base of the pan as needed, roast for about 40-45 minutes.
Remove from the oven. Let it cool for 10 minutes.