Heat about a tablespoon of olive oil in a medium pot. Add the onion and garlic and cook over a medium heat. Add a pinch of salt.
Continue to cook the onion and garlic, stirring occasionally, for about 10-12 minutes. When the onions and garlic are soft and starting to brown, add the cauliflower and the rosemary.
Turn the heat up just a little bit and cook the veggies for another 3-5 minutes. Add just enough vegetable broth to cover the cauliflower. Bring to a boil and reduce the heat so the broth is simmering.
After about 5 minutes, remove the soup from the heat and blend until it is super smooth and creamy looking.