Preheat and prep: Heat the oven to 425°F (220°C).
Line a baking sheet with parchment for easy cleanup.
Season the veggies: Spread the cubed butternut squash, onion, and garlic on the sheet. Toss with olive oil, salt, pepper, cumin, coriander, and cinnamon. Add smoked paprika if you like a hint of smoke.
Roast until tender: Roast for 30–40 minutes, tossing once halfway through, until the squash is fork-tender and the edges are caramelized.
Blend the base: Transfer the roasted vegetables to a blender.
Add 3 cups of broth to start. Blend until completely smooth, venting the lid and covering with a towel to let steam escape.
Adjust consistency: Pour the blended soup into a pot over medium heat. Add more broth as needed until it’s your ideal thickness—velvety but not heavy.
Finish the flavor: Stir in Greek yogurt or light coconut milk, if using.
Add a squeeze of lemon juice. Taste and adjust salt, pepper, and spices.
Garnish and serve: Ladle into bowls and top with crunchy pumpkin seeds, chopped herbs, a drizzle of olive oil, or a swirl of yogurt. Serve hot.