Prep the squash: Heat the oven to 425°F (220°C). Peel the butternut squash, scoop out the seeds, and cut into 1/2-inch cubes. The smaller the cubes, the faster they roast.

Season generously: Toss squash with olive oil, cumin, chili powder or smoked paprika, cinnamon if using, salt, and pepper. Spread on a baking sheet in a single layer.

Roast until tender: Roast for 20–30 minutes, tossing once, until the edges are browned and the centers are soft. You want caramelized bits for flavor.

Sauté aromatics: In a skillet over medium heat, add a drizzle of oil. Cook the sliced onion until soft and lightly browned, 6–8 minutes. Stir in garlic and jalapeño for 1 minute. Season with a pinch of salt.

Combine the filling: Add the roasted squash to the skillet with the onions. Gently mash a few pieces to help the mixture stick together. Stir in cilantro and a squeeze of lime. Taste and adjust seasoning.

Assemble the quesadillas: Warm a clean skillet over medium heat. Lightly oil it. Place a tortilla in the pan, sprinkle with cheese, add a layer of the squash mixture, then more cheese. Top with a second tortilla.

Cook until crispy: Cook 2–3 minutes per side, pressing gently with a spatula, until tortillas are golden and the cheese is melted. Transfer to a cutting board.

Repeat and serve: Continue with remaining tortillas and filling. Slice into wedges. Serve with lime wedges, sour cream or yogurt, salsa, and avocado.

Optional add-ins: If using black beans or corn, fold them into the squash mixture before assembling. For extra tang, sprinkle in crumbled cotija after the cheese.