1. Preheat oven to 350 degrees F. Coat a baking sheet with nonstick spray.
2. Place eggplants cut side down on the baking sheet. Bake until tender (10-15 minutes). Scrape the pulp from the eggplant, reserving the shell. Coarsely chop the pulp.
3. While eggplant is baking, heat oil in a frying pan over medium heat. Saute the onion and garlic until tender (5 minutes).
4. Add the eggplant pulp and tomatoes and cook until eggplant is fully soft (3-5 minutes). Stir in the basil, vinegar, pepper, and salt.
5. Spoon the mixture into the eggplant shells and return to the oven to heat through (5-10 minutes).