Preheat the oven to 325°F.

In a medium bowl combine the cocoa and boiling water and whisk until smooth. Cool.

In a large mixing bowl combine the flour, all but 2 tablespoons of the sugar, baking powder, and salt and beat 1 minute to mix. Make a well in center. Add the oils, egg yolks, chocolate mixture, and vanilla and beat 1 minute or until smooth.

In another large mixing bowl beat the egg whites until frothy, add the cream of tartar, and beat until soft peaks form when the beater is raised. Beat in the remaining 2 tablespoons of sugar and beat until stiff peaks form when the beater is raised slowly. Fold 1 heaping cup of egg whites into the chocolate mixture with a large balloon wire whisk, slotted skimmer, or angel food cake folder. Gently fold in the remaining egg whites until just blended.

Pour into the tube pan (the batter will come to 1-3/4 inches from the top), run a small metal spatula or knife through the batter to prevent air pockets, and bake for 60 minutes or until a cake tester inserted in the center comes out clean and the cake springs back when lightly pressed in the center. Invert the pan, placing the tube opening over the neck of a soda or wine bottle to suspend it well above the counter, and cool the cake completely in the pan (this takes about 1-1/2 hours).

Loosen the sides with a long metal spatula and remove the center core of the pan. Dislodge the bottom and center core with a metal spatula or thin, sharp knife. (A wire cake tester works well around the core. To keep the sides attractive, press the spatula against the sides of the pan and avoid any up-and-down motion.) Invert onto a greased wire rack and reinvert onto a serving plate. Wrap airtight.