Pre heat oven at 200˚C.
Chop the cauliflower into small florets and steam till you can just pierce with a fork, then let cool.
Add cauliflower and onions to a food processor and blitz till fine, then transfer to a nut milk bag or place in fine cheesecloth, and gently press out all of the excess water. Don't skip this step - it helps ensure your pizza isn't soggy.
Meanwhile, add the 6 tablespoons water to the flax meal in a small bowl and let stand for 5 minutes, this is your egg replacer.
In a large bowl, combine all ingredients and use your hands to work them together into a dough. Let stand for 20 minutes to allow flax and chickpea flour to absorb any remaining water.
Line a pizza tray with baking paper, and press dough evenly over the surface.
Fan bake for 25 minutes, at which point, you will want to remove from the oven, slide the pizza onto a plate, flip it back onto the pizza tray, and spread a thick layer of tomato sauce. I have topped mine with fresh rocket,avocado and lemon, but if you want to add other vegetables/mushrooms, now's your chance.
Return to oven for another ten minutes (total oven time, 35 minutes), then enjoy!