Smother the pizza base in ¼ cup of BBQ sauce.
Prepare the cauliflower by removing all the florets and chopping them into bite-sized pieces. Rinse and place them in a baking tray.
Toss the cauliflower in 2 tablespoons of olive oil and a pinch of salt and pepper. Roast at 400F/200C for around 40 minutes, or until soft throughout and crispy on the edges.
Whilst the cauliflower is roasting, slice the onion and throw it in a saucepan with the remaining 1 tablespoon of olive oil.
Cook over a low heat, stirring regularly, for around 30 minutes, or until soft and caramelised. Scatter on top of the pizza base.
Toss the cooked cauliflower in the remaining ¼ cup BBQ sauce and scatter on the pizza base.
Slice or grate the mozzarella - as much or as little as you want - and evenly throw it over the top of the pizza.
Bake at 400F/200C for around 20 minutes, or until the top is golden and the base is crunchy.