3 to 4 cups low-sodium chicken broth or vegetable broth
2 slices gluten-free bread (white or multigrain), cut in ½-inch dice
Ancho chile powder or other dark chili powder
Trim the leafy bottom from the cauliflower. Cut the cauliflower (including the core) into small florets and ½-inch pieces.
Heat 3 tablespoons of oil in a large saucepan over medium heat. Add the onion, season with salt and cook, stirring often, until softened, about 6 minutes. Add 3 cups of broth and bring to a boil. Add the cauliflower, cover, and simmer until fork tender, 8 to 10 minutes. Puree the soup with an immersion blender, adding more broth as needed until smooth. Season with salt and plenty of pepper.
Heat 2 tablespoons oil in a non-stick skillet over medium heat for 2 minutes. Add the bread cubes and cook for 1 minute; toss in the pan and sprinkle generously with chile powder. Cook until bread is hot and beginning to crisp. (Croutons will crisp more as they cool.)
Reheat the soup to piping hot and ladle into bowls. Sprinkle croutons on top and drizzle each serving with a bit more oil.