Preheat oven to 400 degrees Fahrenheit.
Line a large rimmed baking sheet with parchment paper. In a bowl toss the cauliflower with 2 tablespoons of oil, coating the cauliflower. Arrange the florets on the baking sheet in a single layer (use 2 sheets if necessary), and lightly sprinkle with salt. Bake until the cauliflower is cooked through and lightly caramelized, roughly 20 – 35 minutes.

In a soup pot, heat the remaining 1 tablespoon of oil until it shimmers. Add the chopped onion and a pinch of salt. Cook, stirring, until the onion is cooked, and becomes translucent. Don’t overcook.

Add broth, cauliflower and cut up potato to the pot and bring the soup to a simmer, add lid, and allow to cook roughly 20 minutes, or until the cauliflower and potato, are very tender, stirring periodically.

Remove the pot from the heat, remove lid, and allow soup to cool for at least five minutes.

Using a blender or food processor, add vegetables in batches with enough broth to puree the vegetables, but not so much that it becomes too liquid. Pour pureed soup into separate pot, and continue until all of the soup has been pureed. Once everything is pureed, add cream, if using, and adjust the thickness of the soup by adding more stock.

Add butter if using, then add vanilla extract, and 1 tablespoon lemon juice, taste, then add more lemon juice if needed. (I used Meyers’s lemons, which are not as tart as Eureka or Lisbon lemons, which is why I recommend tasting before adding more lemon juice.

Now add the additional flavors you’re using (saffron, chilies, etc.),* stirring well. Let the soup rest until the flavors are well absorbed. Reheat if necessary but don’t allow to boil. Pour into soup bowls and garnish as desired.