Directions

1. Heat the oven to 350 degrees. Sift together the cake flour, 2/3 cup sugar and the salt. Repeat.
2. In the bowl of a standing mixer fitted with a whisk attachment, beat the egg whites with 1 tablespoon cold water, the lemon juice, cream of tartar and vanilla on low speed for one minute. Increase the mixer speed to medium and beat until the whites just hold very soft peaks, one to three minutes. Gradually beat in the remaining 2/3 cup sugar, one tablespoon at a time, on medium speed. At this point, you should have soft, glossy peaks -- do not beat until completely stiff.
3. Gently fold the dry ingredients into the whites in small increments (about an eighth at a time), making sure there are no streaks of flour at the end, but being careful not to over-mix. Pour the batter into an ungreased tube pan and gently spread to level the batter. Bake for 35 to 40 minutes, until a toothpick or cake tester inserted into the middle of the cake comes out clean. Let the cake cool upside down in the pan (set on a bottle or suspended over 4 glasses) for an hour and half or so. Slide a thin, sharp knife around the edges of the pan to loosen the cake and unmold onto a rack. Invert the cake and cool completely.
4. To make the icing, whip the cream with the sugar until it forms soft peaks and fold in the chopped toffee. Ice the cake and refrigerate until read to serve.