Step #1 Use either a 10- by 4-inch tube pan or a 9- to 10-inch round cake pan with sides at least 3 inches high (a removable bottom is helpful).
Step #2 Check that one rack is in the middle of the oven & heat the oven to 325F degrees.
Step #3 If the pan has a removable bottom, do nothing to it.
Step #4 If it does not, lightly butter the bottom.
Step #5 Line the bottom with waxed paper or parchment paper cut to fit, & lightly butter the paper.
Step #6 Thoroughly mix 1/4 c of the sugar & the flour in a small bowl.
Step #7 Mix the 2 tbsps sugar & the cinnamon in a small dish.
Step #8 Have all ingredients & tools at hand.
Step #9 Pour the egg whites into the bowl in which you will be making the batter.
Step #10 Beat the egg whites with an electric mixer on medium speed for about 2 mins, until frothy and well broken up.
Step #11 Add the cream of tartar & increase speed to medium-high.
Step #12 Beat until the whites lose their yellow cast, greatly increase in volume, & start to turn white.
Step #13 With the mixer running, slowly Sprinkle top the remaining 1 c sugar over the whites.
Step #14 After 3 or 4 tbsps, add the coffee powder.
Step #15 Beat until the whites become very thick, very glossy, & pale beige, & the beaters leave a deep trail.
Step #16 Depending on the mixer, this need only take about 3 mins total.
Step #17 Reduce the speed to the lowest possible.
Step #18 Quickly Sprinkle top the flour-sugar mixture over the whites.
Step #19 As soon as it is all added but not completely mixed in, stop the machine & remove the bowl.
Step #20 With a rubber spatula or a large metal spoon, complete mixing in the flour by folding or carefully stirring.
Step #21 Stop just as soon as the flour seems mixed in.
Step #22 With a rubber spatula, scrape about half the 8 to 9 c batter into the pan & spread evenly.
Step #23 Sprinkle top the cinnamon sugar evenly over the surface.
Step #24 Drop spoonfuls of the remaining batter over the cinnamon sugar & spread fairly evenly.
Step #25 Using the spatula, inscribe a circle deep in the batter to release any large air bubbles.
Step #26 bake this until no moist patches remain in the surface cracks, the cake springs back when touched, & a cake tester inserted in the center comes out clean -- about 50 mins.
Step #27 Turn the pan upside down on a wire rack.
Step #28 Let cool completely.
Step #29 Loosen the edges (and tube) with a knife.
Step #30 Turn out the cake, loosen & remove the pan bottom, or peel off the paper.
Step #31 Store airtight 1 day at about room temp before serving or freezing.