Preheat the oven to 190 C / Gas 5. Make sure that your 26cm tube cake tin is clean and dry. Sieve together the flour, cornflour and 150g of the sugar; set aside.
In a large bowl, beat the egg whites with vanilla, cream of tartar and salt to medium stiff peaks. Gradually add the remaining sugar while continuing to beat to stiff peaks. When the egg white mixture has reached its maximum volume, fold in the sieved ingredients gradually, one third at a time. Do not overmix. Pour batter into prepared tin.
Bake for 40 to 45 minutes in the preheated oven, until the cake springs back when touched. Balance the tin upside down on the top of a bottle, to prevent decompression while cooling. When cool, run a knife around the edge of the tin and invert onto a plate.