Preheat the oven to 375 degrees F. Grease a 9-inch springform pan with cooking spray and set aside.
Melt the chocolate chips in a double boiler or microwave until melted and smooth. Set aside to cool slightly.
In the bowl of an electric mixer, beat the egg whites on medium speed for 1 minute. Add the cream of tartar, salt, and sugar and continue beating until stiff peaks form (about 4 minutes).
Gently fold in the melted chocolate into the eggs whites using a rubber spatula, taking care not to deflate the egg whites too much.
Pour the batter into the prepared springform pan and bake for 40 minutes or until center is just set (it will still be jiggly).
Let the cake cool completely before unmolding and serving. Enjoy!