2. Spread the eggplant, pepper and onion on the baking pan and bake, flipping twice, until the vegetables have wilted and browned lightly, about 45 minutes. Cool to room temperature.
3. Place the roasted vegetables in a food processor with the vinegar and basil and process until roughly chopped. Add the walnuts and capers and process again until the mixture is thick and coarsely blended. Season with salt and pepper to taste. Makes about 2 cups roasted vegetable mixture.
4. Cut the top, or stem end, from each tomato. Using a knife point, loosen the insides of each tomato, and then scoop out the seeds and juices with a small spoon, leaving just a tomato shell.
5. With a small spoon, place a generous tablespoon of filling in each tomato, mounding it over the top. Alternately, place the filling mixture in a zip-seal plastic bag. Seal the bag then make a small diagonal cut on one of the lower corners. Press the mixture through the hole and into the tomatoes.