Sift the flour, 1 cup sugar, baking powder, and salt together in a bowl. Make a well in the center of the flour mixture. Pour the coffee, oil, and egg yolks into the well; beat well by hand until the batter is smooth with no lumps.
Beat egg whites with the cream of tartar in a large bowl until foamy. Gradually add 1/2 cup sugar, continuing to beat until stiff peaks form. Lift your beater or whisk straight up: the egg whites should form a sharp peak that holds its shape. Fold the batter into the egg whites; pour into a non-stick Bundt(R) fluted tube pan.
Bake in the preheated oven until a toothpick inserted into the center comes out clean, about 60 minutes. Cool in the pans for 10 minutes before removing to cool completely on a wire rack. Loosen the sides with a knife and release the cake onto a serving platter.