Preheat oven to 425 degrees.  Toss onion, cauliflower and garlic with olive oil and a sheet pan.  Season with salt and pepper. Roast vegetables until tender and caramelized, stirring occasionally, about 30-35 minutes.

Transfer roasted vegetables to a dutch oven or large saucepan.  Add broth, water, rice and bay leaf. Bring to a boil and reduce to a simmer.  Continue to cook until rice is tender, about 20 minutes.

While the soup simmers, make the Croutons. Toss bread cubes with olive oil on a rimmed baking sheet. Season with salt and pepper. Bake until toasty golden brown, about 7-9 minutes. Remove from the oven and set aside.

Remove bayleaf from the soup.  Puree soup in two batches in a blender until smooth (or use an immersion blender if you have one).  Return soup to pot.

Bring soup back to a simmer over low heat.  Add lemon juice and season to taste with salt and pepper.  Serve with Croutons, a drizzle of olive oil and a shower of chopped fresh chives.