Preheat oven to 425°F (220°C).

Slice squash in half lengthwise, scoop out seeds, then slice each half into 1-inch-wide rings. Cut rings into half-moon shapes.

Toss squash with olive oil, salt, pepper, and chili if using. Spread on a rimmed baking sheet.

Roast for 40-50 minutes until tender and golden, testing doneness by piercing with a knife.

While roasting, melt butter in a small saucepan over medium heat. Cook, swirling occasionally, until browned and foaming (~5 minutes).

Remove from heat and stir in pistachios, cumin, cinnamon, chili (if using), and flaky salt. Set aside.

Mix yogurt, mint, lemon juice, and salt in a bowl.

To serve, spread yogurt mixture on a platter, arrange roasted squash on top, drizzle with spiced buttered pistachios, and finish with flaky salt and freshly ground pepper.