Place a steamer insert into a saucepan and fill with water to just below the bottom of the steamer. Bring water to a boil. Add cauliflower, cover, and steam for 7 minutes. Let cool and finely chop.
Place chopped cauliflower, carrots, tomatoes, onion, and cilantro in a bowl. Pour lime juice on top and season with salt. Cover and chill for at least 30 minutes. Serve garnished with avocado slices.
