Preheat the oven to 200°C/gas mark 6. Whizz the cauliflower in a food processor until fine and grainy. Place the cauliflower in a microwaveable bowl and cover with clingfilm. Pierce a few times with a fork and cook on high for 5 minutes until softened. Tip on to a muslin square or clean tea towel and leave to cool a little.
Once the cauliflower is cool enough to handle, scrunch up the tea towel and squeeze as much liquid as you can out of the cauliflower, then transfer to a clean bowl. Stir in the parmesan, ground almonds and eggs and season to taste.
Line a baking tray with baking paper and heap the cauliflower mix into the centre of the tray. Use a spoon and your hands to spread out into a 30cm circle, making it a little thicker at the edges to create a ‘crust’. Bake for 15-18 minutes until golden brown and starting to crisp a little at the edges. Set aside to cool slightly. Turn the oven up to 240°C/gas mark 9.
Meanwhile, bring a medium pan of water to the boil. Trim the ends of the broccoli and add to the pan. Cook for 2 minutes, then drain. Toss with the olive oil, garlic and lemon zest. Spread the tomato paste on the cauliflower pizza base, avoiding the crust. Scatter over the broccoli, then top with the anchovies. Return to the oven and bake for 13-15 minutes. When cooked, serve on a chopping board to cut easily.