Brush a 9 x 2-inch round cake pan with melted butter or spray generously with cooking spray. Line the bottom of the pan with parchment paper. Preheat oven to 340° F.

Melt butter and chocolate in a large bowl on top of a pot of barely simmering water. Set aside but keep warm.

In a clean bowl with a clean whip, whip the egg whites on medium speed until foamy. Continue beating, gradually drizzling in the first 1/3 cup of sugar until the peaks are almost firm, yet tip over just a bit. Do not whip until the egg whites are dry.

Transfer to a bowl and set aside.

Beat the egg yolks with the remaining sugar in the mixing bowl until the eggs are very thick and pale yellow and the mixture falls from the beaters like a “ribbon.”

Fold the yolks into the butter and chocolate mixture. Gently fold in the egg whites.

Pour into the prepared pan.

Bake 20 to 25 minutes, until the torte is just set in the middle. The cake will rise to the top of the pan and deflate as it cools. Let cool in the pan about 2 hours.

Gently invert onto a cardboard or something flat. (I use the bottom of a springform pan.) Remove the parchment paper and immediately re-invert onto a serving platter. Using a fine sieve, dust lightly with cocoa powder. If you wish, cover the center 6 ½-7 inches with something round and dust a white powdered sugar outer ring.