Heat olive oil in a large saucepan or soup pot over medium heat. Add chopped onion and garlic, and cook 3-4 minutes, stirring often until onion is translucent.
Add carrots and celeriac root. Sprinkle with pinch of salt. Cook, stirring often, for 1 minute. Don't let the carrots or onion brown.
Pour in vegetable broth. Bring to a boil. Add ginger, cover and cook for at least 20 minutes, or until carrots and celeriac are tender.
Remove from the heat. Puree in blender until very smooth. Return the soup to the saucepan and stir in turmeric, cumin and cayenne pepper. Add more salt to taste. Pour the soup into bowls and serve.
Garnish with cumin and/or parsley.
Keep refrigerated up to 3 days. Can be frozen up to 3 months.
I used US cup (240ml) as a measure.