1/3 cup olive oil
1 1/2  lemons, juiced
2 tablespoons tomato paste
1 teaspoon salt
1 teaspoon chili powder
1/2 teaspoon cumin
1  pinch of {black pepper}

2  ripe avocados
2  small tomatoes
1 cup pitted black olives
1  head Bibb lettuce

Dressing:
Place all ingredients in a blender, and blend on a low speed for 1 minute.

Salad:
Cut avocados in small pieces and tomatoes in wedges. Place in a medium bowl along with the olives. Pour the salad dressing on and mix lightly. Marinate for at least 30 minutes in the refrigerator. Serve on a bed of lettuce.