In a large pot, heat the olive oil over medium heat. Add the chopped onion and sauté until translucent, about 5 minutes.
Add the diced carrots, minced garlic, and grated ginger to the pot. Stir and sauté for about 5 minutes until the vegetables begin to soften.
Pour in the vegetable broth and bring the mixture to a boil. Reduce heat, cover, and let it simmer for about 20 minutes, or until the carrots are tender.
While the soup is simmering, drain the soaked cashews and rinse them under cold water.
Once the carrots are soft, remove the pot from heat. Stir in the soaked cashews, salt, and pepper.
Using a blender or immersion blender, carefully blend the soup until smooth and creamy.
Reheat gently over low heat if needed, and stir in the lemon juice. Adjust seasoning as desired.
Serve hot, garnished with fresh cilantro if using.