Arrange a rack in the bottom of the oven and another one in the middle. Fill a baking pan with water and place on the bottom rack. Heat oven to 350°F and let water heat as oven heats.

Butter an 8-inch round cake pan and line the bottom with parchment paper. Butter the parchment paper.

Combine chocolate, butter, and granulated sugar in a metal bowl set over simmering water. Stir frequently until the chocolate is completely melted and mixture is smooth.

Remove the chocolate from the heat and whisk in the cinnamon, the vanilla and almond extracts, the eggs, cocoa powder, and a pinch salt. Pour batter into cake pan.

Place cake pan in the oven and bake until the edges are set and a toothpick comes out with a few moist crumbs, about 35 minutes.

Set cake on a wire rack to cool for 10 minutes then invert onto a cake plate so that the bottom is now the top. Allow to cool completely then sprinkle with confectioners sugar and serve. (Note: the cake will sink quite a bit once out of the tin: this is normal and adds nicely to the dense, rich texture.)