-
Preheat the oven to 375ºF. In a stand mixer fitted with the whisk attachment (or with a hand mixer) whip the egg whites until foamy. Add the cream of tartar and salt and whip until the mixture forms soft peaks. With the mixer running, slowly add in 1 cup of sugar and whip until the mixture forms stiff peaks, about 30 seconds.
-
In a small bowl, stir together the instant espresso powder and hot water.
-
Using a sieve set over a large bowl, sift the cake flour, remaining 1/2 cup sugar, and pumpkin pie spice.
-
Using a spatula, carefully fold the flour mixture 1/3 at a time into the egg white mixture. Fold in the espresso-water mixture and the vanilla extract.
-
Spoon the batter into an ungreased 9- or 10-inch tube pan and spread it evenly. Bake until golden-brown, 30 to 35 minutes.
-
Remove the cake from the oven and invert it over a wine bottle (insert the bottle through the hole in the middle of pan and flip the cake over on top). Let cool to room temperature. Run a knife around the cake to loosen it, then turn it out onto a serving plate.