1 large head of cauliflower, just cover the cut cauliflower with water and boil on medium-high heat for around 30 minutes without a lid (much of the water will boil off and the cauliflower will be very tender).
Place the cauliflower in a food processor or blender. Add the remaining boiled water until you get your desired soup consistency.
Peel and de-seed a large cucumber. Add to the food processor. Blend well.
Add two avocados to the food processor. Add 2-4 tsp of lemon juice. Blend well. Add salt to taste.
Serve warm or cold.