Preheat the oven to 350F. Grease 4 small ramekins and set aside.
In a double-broiler melt the chocolate and butter together until smooth.
In a large bowl whisk the eggs, sugar, rum, cinnamon and cayenne. Add 2 tablespoons of the melted chocolate into the egg mixture and whisk well. Add remaining the remaining melted chocolate and the flour. Whisk until thoroughly combined.
Evenly fill the ramekins with the batter. Bake until the edges are set and the middle appears cooked but is soft to the touch, about 25 minutes.
Let the cakes cool for 2 to 3 minutes. Warm the dulce de leche in the microwave for 15 seconds, stir and repeat until liquid.
Flip a cake over onto a small dish. Using a pastry bag, pipe some dulce de leche into the cake from the side. Dig in and watch the dulce de leche ooze out after your first bite!