Prepare a nine-inch springform pan by lining the bottom with Gefen Parchment Paper and greasing the sides. Preheat the oven to 350 degrees Fahrenheit.
In the bowl of a stand mixer, cream the butter or margarine and half a cup of sugar together until light and fluffy.
Add the egg yolks and beat until combined.
Add the salt, vanilla, orange zest and juice and the cocoa powder and mix together.
Carefully add the melted chocolate and mix on medium until it’s been incorporated with the rest of the ingredients. Set aside.
Using a clean bowl and the whip attachment, whip the egg whites on high until soft peaks form. Slowly add the remaining half cup sugar and continue to whip on high until stiff peaks form.
Add one third of the egg whites to the chocolate mixture and fold together.
Continue folding in the rest of the whites in two more batches. The batter may look a little lumpy, but that’s ok.
Pour into the prepared springform pan and bake for 45 minutes, until a crust has formed and the batter no longer jiggles when you shake it.
Remove from the oven and cool. Carefully run a thin, sharp knife around the cake. Release the sides of the pan and set the cake, still on the pan’s base, onto a serving dish. Sprinkle the top with icing sugar and serve with fresh fruit and whipped cream or non-dairy topping.