Separate the egg. Beat egg white until stiff. Mix egg yolk, flour and salt. Carefully fold into the beaten egg white. Melt the fat in a pan. Add the egg mixture, smooth it down and let it simmer in a closed pan at low heat.
Mix orange and grapefruit fillets with orange juice, sweetener and cinnamon. Mix yoghurt and vanilla pulp. Arrange omelette with fruit and yoghurt on a plate. Sprinkle with pistachios.