Heat the olive oil in a large pot over medium heat. Add the chopped onion and cook until it softens, about 5 minutes.
Stir in the carrots, grated ginger, turmeric, cumin, and coriander. Cook for 2 minutes until the spices smell fragrant.
Pour in the vegetable broth, salt, and black pepper. Bring the mixture to a boil, then reduce to a simmer. Cover and cook for 20 minutes until the carrots are tender.
Remove the pot from the heat. Use an immersion blender to puree the soup until smooth. Return the pot to low heat to keep warm.
In a small bowl, mix the yogurt with the remaining teaspoon of cumin. Ladle the soup into bowls and add a spoonful of the cumin yogurt on top.