This is not exactly authentic, but I wanted to add a vegetable to my tortilla soup, to make it more of a dinner in a bowl, so I decided to shave cauliflower, toss the ricelike pieces with oil and chili powder, and roast it. I loved the addition of the spicy roasted cauliflower to each bowl of soup, along with the tortilla crisps that I toasted in the microwave rather than frying. You can make this soup even more substantial by adding eggs (see the variation that follows the recipe).
02Meanwhile, heat remaining olive oil in a heavy soup pot over medium heat and add onion. Cook, stirring often, until tender, about 5 minutes. Add a generous pinch of salt and chili powder and stir together for a minute, then add garlic and continue to cook, stirring, for another minute, until fragrant. Add tomatoes, stir well to deglaze bottom of pot, and cook, stirring often, until tomatoes have cooked down and smell fragrant, about 10 minutes. Add salt to taste. Add stock or broth, bring to a simmer, cover and simmer over low heat for 30 minutes.
03While soup is simmering, toast tortilla strips in batches in microwave. Place in a single layer on a plate and microwave at full power for 1 minute. Turn strips over and microwave for another minute. Repeat if necessary for 30 seconds, or until crisp and light brown. Set aside.
04Using an immersion blender, blend soup until smooth. Bring back to a simmer and stir in cilantro. Simmer for 1 minute. Taste and adjust salt. Stir in lime juice.
05Distribute toasted tortilla strips and cauliflower “rice” among soup bowls and ladle in the soup. Top with crumbled cheese and serve.