Puree quartered tomatoes and onions in a food processor until smooth.

Heat 3 tablespoons of vegetable oil in a large saucepan over medium heat.

Add chopped tortillas and finely chopped garlic and sauté for 2 minutes.

Add the tomato-onion puree, chicken broth, tomato paste, chopped cilantro, ground cumin, chili powder, and bay leaves to the saucepan and bring to a boil.

Reduce heat and simmer for 30 minutes.

Season the soup to taste with salt.

Strain the soup through a coarse sieve, pressing on the solids with the back of a spoon.

Heat the remaining 1/2 cup of vegetable oil in a skillet over high heat.

Add the tortilla strips and cook until crisp and golden, about 3 minutes.

Transfer the tortilla strips to paper towels to drain.

Bring the strained soup to a simmer.

Ladle the soup into bowls.

Serve, passing tortilla strips, diced chicken, diced avocado, shredded cheddar cheese, and sour cream separately for topping.