Preheat the oven to 375 degrees. Grease a 9 inch spring form pan. Place the chocolate and butter in a heatproof bowl in a double boiler to melt the chocolate, or use the microwave on medium power for about 2 minutes. Stir it occasionally until melted.
Stir in the rum or brandy if using it, and almond extract, and salt. Set aside.

In a large bowl, whisk the egg yolks with ½ cup of the sugar until well blended. Stir in the chocolate mixture. Set aside.
In a clean dry bowl, with an electric mixer, beat egg whites and cream of tartar at medium speed until soft peaks form. Gradually sprinkle in the remaining ¼ cup of sugar, beating at high speed until peaks are stiff but not dry. Sprinkle the almond flour over the chocolate batter and scoop about one quarter of the egg whites on top. Fold with a large rubber spatula until partially blended.
Scrape the remaining egg white into the bowl and fold the batter into the prepared pan. Bake it for 25-30 minutes or until a toothpick
inserted in the middle is still moist and gooey. Set the pan on a rack to cool. The cake rises like a soufflé during baking, then falls as it cools, sometimes leaving a faintly crusty higher rim around the edges. Level the torte before removing it from the pan, as follows. Remove the cake from the pan, and let it cool.