Preheat the oven to 375°F. Line two baking trays with parchment paper.
Remove stems from the dried chiles using kitchen shears. Cut them lengthwise and open them flat. Warm a dry skillet over medium heat and toast the chiles for 1–2 minutes per side, until fragrant and pliable. Add one tortilla to the skillet and toast on both sides until puffed and aromatic.
Transfer the toasted chiles and tortilla to a blender. Pour in the fire-roasted tomatoes and blend until smooth.
In a large pot or Dutch oven, warm the avocado oil over medium heat. Add the chopped onion (reserving ⅓ cup for garnish) and sea salt. Cook for 8 minutes, stirring occasionally, until the onions are soft. Stir in the cumin and oregano and cook for 30 seconds until aromatic. Pour in the blended chile-tomato mixture and stir for 2 minutes.
Incorporate the grated garlic, vegetable broth (or water), and black beans. Simmer for 20 minutes. Add the corn kernels and continue simmering for another 10 minutes.
Meanwhile, slice the remaining 7 tortillas into thin strips. Spread them across the lined baking sheets. Drizzle with avocado oil and sprinkle with sea salt. Toss to coat and arrange in a single layer. Bake for 10–15 minutes, or until golden and crisp.
If the soup thickens too much, adjust the texture with a splash of broth or water. Taste and fine-tune the seasoning with additional salt or pepper.
To serve, ladle the soup into bowls. Garnish each with the crispy tortilla strips, reserved diced onion, avocado chunks, radish slices, cilantro leaves, and Cotija cheese. Offer lime wedges on the side for a fresh citrus finish.