Preheat your oven to 400°F (200°C).
Place the halved butternut squash, onion quarters, and halved carrots on a baking sheet. Drizzle with olive oil, sprinkle with salt and pepper. Roast in the oven until tender and slightly caramelized, about 40-45 minutes. In the meantime, soak the cashews in a bowl of water. Remove from the oven and let cool slightly.
In a blender, combine the roasted butternut squash (I included skin but you can scoop flesh out of the skin), roasted onions, roasted carrots, chopped ginger, soaked cashews, vegetable bouillon cubes, and water. Add lemon juice, salt, and pepper to the pot. Stir well to combine. Adjust seasoning according to your taste preferences. If needed, do this in batches. NOTE: I like to use bouillon cubes because I can control how much liquid I add for a consistency that I like and not run out of stock.
Blend until smooth and creamy.
If needed to warm up or keep warm, pour the blended mixture into a large pot. Place the pot over medium heat.
Pour into bowls and garnish.