Preheat the oven to 350°. Make sure the baking rack is in the middle of the oven.
To melt the chocolate, place the rum and chocolate in a saucepan. In a slightly larger pan, fill it halfway with water and set the small saucepan with chocolate on top of it.
Place pans on the stovetop and bring the water to a simmer. Mix chocolate with a rubber spatula and stir until mostly melted. Once it is almost completely melted, remove it from the stove and allow the last part of the chocolate to melt slowly.
Measure out all the rest of the ingredients listed.
Cream the butter and sugar together until soft and fluffy with a handheld or Kitchenaid mixer.
Beat in the 3 egg yolks and set aside.
To whip the 3 egg whites, place them in a clean and dry mixing bowl and whip them at a low speed for a moment or two until the egg whites begin to foam.
Then add the cream of tartar and salt to the mixture and gradually increase the beating speed to fast. As soon as the egg whites hold their shape in a soft mass, beat in the two tablespoons of sugar.
Keep whipping the egg white mixture until the whites are stiff. To test the whites, lift the beaters out of the mix, and the egg white should point up with a little curling tip at the end. Set aside.
The texture of the whipped whites should be smooth and shiny.
Stir the melted chocolate so that it's smooth and creamy. You may have to reheat the chocolate if it has cooled too much.
Add the melted chocolate into the butter, sugar, and yolk mixture. Stir in the almond extract and flour.
With a rubber spatula, stir in about ¼ of the beaten egg whites to loosen up the batter. Once mixed thoroughly, add the rest of the whipped whites to the batter. Delicately fold the whites in by cutting straight down through them to the bottom of the bowl. Drawing the spatula quickly toward you against the edge of the bowl, turning, and lifting it out, you bring the batter up over the egg whites and mix them. The whole process should not take more than a minute.
Turn the batter into the prepared cake pan.
Bake for 20 minutes
You want this cake moist so underbake the cake.
Remove the baked cake from the oven and place on a baking rack. Cool for 10 minutes, then remove from the pan and cool on a rack. Let the cake cool for two hours before icing.