Preheat oven to 350º.
Line a 9-inch round cake pan with parchment.
Melt the chocolate, butter and rum together in double boiler,whisking until smooth then setting aside to cool down.
Next mix egg yolks and 1/2 cup sugar in a mixing bowl and whip on high, then gently mix in the lukewarm chocolate mixture.
Add the flour salt mixture, blending well.
Whip the egg whites in a clean bowl until frothy, then whip on high to form soft peaks. Add the remaining sugar and whip until stiff peaks form then
gently fold the egg whites into the chocolate batter with spatula until no white streaks remain.
Spread batter into the round baking pan.
Bake 35 minutes, just until a sharp knife into center comes out clean.
Place parchment paper on a baking sheet and after running a sharp knife around the inside edge of the cake pan to loosen the cake hold a wire rack over pan and invert cake pan and rack, remove cake pan and set cake on rack on parchment covered cookie sheet.
*For the chocolate glaze bring cream to a boil then remove from heat and add the chocolate, whisking until smooth.
Let glaze cool until it slightly thickens but is still pourable(30-40 minutes), then slowly pour the glaze over the cake letting it drip down to completely cover with chocolate.
When the glaze stops dripping carefully use a large spatula to transfer cake to a pretty cake platter....let the chocolate set up before cutting cake with a hot knife.
*serve with whipping cream or vanilla ice cream