Preheat the oven to 400 degrees.
Cut the eggplant, bell pepper, and onion into
1-inch cubes. Toss them in a large bowl with
the garlic, olive oil, salt, and pepper. Spread
them on a baking sheet. Roast for 45 minutes,
until the vegetables are lightly browned and
soft, tossing once during cooking. Cool
slightly. Place the vegetables in a food
processor fitted with a steel blade, add the
tomato paste, and pulse 3 or 4 times to blend.
Taste for salt and pepper.