Step 1

Finely grind coriander, cumin, fennel, oregano, and paprika in a spice mill or with a mortar and pestle.

Step 2

Heat oil in a large nonstick skillet over medium-high. Add mushrooms in a single layer and cook, undisturbed, until very crisp underneath, about 3 minutes. Turn mushrooms over and season with salt. Continue to cook, tossing every minute or two, until browned all over, about 5 minutes. Sprinkle spices over and add garlic and butter; season with more salt. Cook, tossing often, until fragrant, about 1 minute. Transfer to a plate and let cool slightly. Wipe out skillet; reserve. Season mushrooms with more salt if needed.

Step 3

Place reserved skillet over medium-low heat. Lay a tortilla in pan and top one side with half of cheese and half of mushrooms. Fold tortilla up and over filling. Repeat with remaining tortilla, cheese, and mushrooms to make another quesadilla. Cook, turning once, until golden and cheese is melted, about 5 minutes. Transfer to plates and top with onion, cilantro, and hot sauce.