Preheat the oven to 190 degrees C. Wash ring tin in hot soapy water to ensure it is totally grease free. Let dry completely.
Sift together the flour and 3/4 cup sugar. Set aside.
In a large bowl beat the egg whites, vanilla, cream of tartar and salt until soft peaks form. Peaks should be soft enough so they bend over slightly at the tips. Gradually add the remaining 3/4 cup sugar while continuing to whip to stiff peaks. Fold in the sifted ingredients gradually, one third at a time. Do not overmix. Put the mixture into the ring tin.
Bake for 40 to 45 minutes in the preheated oven until the cake springs back when touched. Balance the ring 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.