Tacos With Homemade Salsa and Guacamole

Ingredients

• 2 tablespoons extra-virgin olive oil
• 1 onion, finely chopped
• 1 eggplant (10 ounces), cubed
• 1 butternut squash (1 1/2 pounds), halved, seeded, peeled and cubed
• 1 large zucchini (6 ounces), cubed
• 1/4 teaspoon chili powder
• 1/2 teaspoon ground cumin
• 1 garlic clove, crushed
• 1 can (14 1/2 ounces) tomatoes
• 1 large ripe avocado Juice of 1/2 lime
• 3 ripe tomatoes, diced
• 1/2 red onion, finely chopped
• 1/4 cup chopped cilantro
• 8 taco shells
• 8 ounces plain low-fat yogurt