Place the quinoa in a pan with the water and bring it to the boil. Reduce the heat to simmer and cook for 15 minutes. Remove from the pan and transfer to the bowl to cool slightly. Stir through the coriander leaves, grated cucumber, lemon zest, one teaspoon of caviar and some cracked pepper.
Place a round metal cutter around 7cm deep onto the centre of a serving plate and fill it with the quinoa, to about 2cm from the top. Arrange a layer of smoked salmon over the quinoa and follow with a layer of avocado. Top with a few extra caviar beads. Carefully lift the ring of the plate and repeat until you have completed all four.