While these tostadas may not exactly be traditional, they are tasty. The chipotle pepper gives the sauce a smoky kick. If you aren't so keen on heat, cut the amount to just 1/2 of a chipotle pepper (about 1 teaspoon minced). For a simple shortcut, feel free to use pre-cut cauliflower, figuring you'll need 6 yo 7 cups for the recipe. The tostadas are fairly light on the appetite, so consider serving pinto or black beans on the side.
Cut the cauliflower into small florets and pile onto a baking sheet. Drizzle with olive oil and sprinkle with chili powder, cumin, and 1 teaspoon of the salt. Toss well and spread out. If the cauliflower is crowded, use a second baking sheet. Bake until tender and lightly browned, about 30 minutes.
Lay tortillas on 1 to 2 large baking sheets (slightly overlapping is ok) and bake until crispy, about 17 minutes.
To assemble, spread avocado onto the tortillas. Top with the cauliflower, a drizzle of the chipotle sauce, a few pickled onions or pickled jalapeños, and a little bundle of cabbage. Serve while the cauliflower is still warm.
Make pickled onions by stirring 1 tablespoon sugar and 1 teaspoon kosher salt into ¼ cup red/white wine vinegar in a small bowl until dissolved. Add ½ medium thinly sliced red onion. Leave to macerate for a good 20 minutes. Alternatively, use store-bought sliced pickled jalapeños.