Begin by roasting the cauliflower. Pre-heat oven to 450 degrees. Toss the cauliflower with olive oil, salt, cumin, smoked paprika and cayenne on a baking sheet then roast until golden brown, about 20 minutes.
While the cauliflower is roasting, make the chipotle sauce by whisking together the tahini, chipotle peppers, garlic and salt in a small bowl. Gradually add warm water, 1 tablespoon at a time, until you've reached desired consistency. Check for seasoning and add a little extra salt if needed.
Warm the tortillas on a hot griddle drizzled with olive oil. Heat for 90 seconds per side, flipping once. Keep tortillas warm by covering with a towel until you're ready to begin assembling tacos.
To assemble tacos, fill each tortilla with roasted cauliflower and drizzle with chipotle tahini sauce. Top with optional garnishes to serve.
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Notes
To keep the chipotle tahini sauce mild, remove seeds and pith from the chipotle peppers in adobo sauce.