Preheat the oven to 275 degrees F. Line a baking pan with parchment paper. Beat the egg whites and the cream of tartar until they reach soft peaks.
Add in the sugar and beat until stiff and glossy. Carefully add the cocoa powder and powdered sugar and mix well.
Put the meringue in a piping bag fitted with a round tip. Make kisses all around the baking sheet. Bake for about 1 hour, turning the pan halfway through. Turn off the heat and leave the pan inside until the oven cools. You will have more kisses than needed for the pie, but I love adding them to ice cream, cereal, or even snacking on them on their own!
Notes
Its best to use room temperature egg whites.
Thoroughly clean and dry all your tools that will touch the egg whites and lightly brush with fresh lemon juice. This is to remove any traces of oil or fat which can stop the egg whites from whipping properly. If any yolk gets into the egg white, discard and start over.