In a large bowl, toss cauliflower and leeks with grapeseed oil, tumeric and cumin. Spread cauliflower and leeks on baking sheet, add coarse salt and roast in the oven for 15 - 20 minutes, until leeks start to brown.
Transfer roasted cauliflower and leeks to a food processor. Add broth and coconut milk and blend well. You may add more broth or water to get to the desired consistency. Pour mixture into a saucepan and heat over low heat until ready to serve.
To make gremolata, zest lemon into a food processor. Add parsley, garlic and olive oil. Blend until well combined.
Ladle soup into bowls. Add a spoonful of gremolata to each bowl and serve immediately.