This roasted cauliflower soup recipe is the perfect balance of texture and flavor. Lemon juice adds brightness while crushed red pepper adds a touch of heat. Toasted nuts bring a bit of crunch to this creamy soup.
Preheat oven to 425°F. Combine cauliflower, shallots, garlic, cumin, 2 tablespoons oil and 1/4 teaspoon salt on a large rimmed baking sheet; toss until fully coated. Spread in an even layer. Roast for 15 minutes; remove and discard garlic. Stir the vegetables and continue roasting until caramelized and tender, about 10 minutes more.
Reserve 1/2 cup roasted cauliflower florets for garnish. Working in batches, combine the remaining cauliflower mixture, warm broth and butter in a blender (use caution when blending hot liquids). Secure the lid on the blender and remove the center piece to allow steam to escape; place a clean towel over the opening. Process until smooth, about 30 seconds. Transfer the mixture to a large saucepan. (Alternatively, combine the cauliflower mixture, warmed broth and butter in a large saucepan. Using an immersion blender, process until smooth, 5 to 7 minutes.) Bring the soup to a simmer over medium-low heat, stirring occasionally. Remove from heat; stir in lemon juice and the remaining 1/4 teaspoon salt.
Divide evenly among 4 bowls; top with the reserved cauliflower florets and sprinkle with pine nuts (or almonds). Drizzle with the remaining 1 tablespoon oil. Garnish with crushed red pepper and oregano, if desired.
Refrigerate soup (Steps 1-2) for up to 5 days or freeze for up 2 months. Reheat and add garnishes (Step 3) when ready to serve.