Grease the inside of 2 ramekins with butter (sides and bottom).
Melt chocolate and butter together.
Mix eggs in a bowl with electric mixer.
Add almond flour, vanilla and cinnamon.
Add chocolate/butter mixture and mix well.
Taste and add sweetener if desired.
Divide into the 2 ramekins.
Bake at 350 for 9-10 minutes. The top should be 'set' but the cake should still jiggle when you shake it.
Remove from the oven and let sit for 5 minutes.
Gently run the tip of a sharp knife around the circumference of the cake. Place a small plate upside down on top of the ramekin, and carefully turn it over, releasing the cake onto the plate.
Garnish with fresh fruit and whipped cream if desired.