Preheat oven to 450°F (230°C).

In a large bowl, toss together cauliflower, onions, garlic, turmeric, paprika, cumin, salt, pepper, and olive oil until evenly coated.

Spread the seasoned vegetables onto a baking sheet and roast for 25-30 minutes, or until golden brown.

In a large saucepan, bring the broth to a boil.

Add the roasted vegetables and reduce heat to simmer for 5-10 minutes.

Stir in the orange zest and juice.

Using a blender or hand blender, puree the soup until smooth.

Taste and adjust seasoning if necessary.

Serve hot, garnished with additional orange zest if desired.