1. Lay out the ham slices on a baking sheet lined with parchment and bake in the middle of the oven until crisp for approx. 10 min. at 200°C (fan oven). Cool on a rack.
2. Bring the water to a boil in a heavy-bottomed saucepan and add the cauliflower. Cook over a medium heat, covered, for about 10 min., stirring occasionally.
3. Drain the cauliflower in a sieve, rinse with cold water, then drain well. Spread the cauliflower out on a tea towel, roll it up and wring out any remaining water.
4. Whisk the eggs in a bowl, then add the cauliflower, cheese, oregano and salt.
4. On a baking sheet lined with parchment, spread half the mixture in a circle (approx. 30 cm in diameter). Repeat the process with the rest of the mixture and bake the crusts on the bottom rack – until golden for 25-30 min. at 200°C (fan oven).
5. Remove the crusts from the oven. Spread them with tomato sauce and bell peppers, then finish baking them for 10 min. at 200°C (fan oven).
6. Meanwhile, toss the rocket with the lemon juice. Break the crispy ham into smaller pieces and sprinkle on the finished pizzas along with the rocket. Serve immediately.