Preheat the oven to 190°C/ gas mark 5.
1) Brush both sides of each tortilla with oil, using one tablespoon of the oil. Cut the tortillas in half, then cut each half into 1/2-cm wide strips. Arrange the strips on a baking tray, sprinkle with the salt, and bake until crisp and golden, about 12 minutes. Remove from oven and set aside.
2) Heat the remaining one teaspoon of oil in a large heavy skillet over medium heat. Add the onion and cook for five minutes, stirring occasionally, until onion is soft and translucent. Add the garlic, jalapeno, cumin, and oregano and cook for one minute more. Add the broth and tomatoes, bring to the boil, then reduce the heat to low and simmer for about ten minutes. Stir in lime juice.
3) Remove the pan from the heat and puree with an immersion blender or in two batches in a regular blender until the soup lightens in colour but chunks of tomato remain, about 30 seconds.
4) Serve the soup topped with the tortilla strips, a dollop of soured cream, and a sprinkle of coriander.