How to Make It
Preheat oven to 375°F. Set aside an ungreased 10- inch tube pan. Place espresso in a cup, add boiling water and stir until smooth. Stir in vanilla and set aside.
Sift flour and 3/4 cup of the sugar onto a sheet of wax paper; sift again into a bowl and whisk together.
Using an electric mixer, beat egg whites at low speed for 1 minute. Beat in cream of tartar and salt, gradually increasing speed to medium, for 1 minute. Very slowly sprinkle in the remaining 3/4 cup sugar. Drizzle in cooled espresso and continue beating at medium speed until whites are stiff but not dry.
Sift about one-third of flour mixture on whites and fold in. Repeat folding in 2 more batches. Pour batter into pan. Bake until a tester comes out clean, 40 to 45 minutes.
Invert cake onto feet of pan (or place center tube over a bottle) to cool completely. Cut around center tube and side of pan with a thin, sharp knife, invert cake, and remove pan. Place cake right side up on a platter and drizzle Fudge Glaze over top.