Preheat your oven to 350°F (175°C). Grease a 9-inch round cake pan and set aside.

In a small saucepan over medium heat, combine the granulated sugar and water. Stir until the sugar dissolves, then let it boil without stirring until it turns a golden caramel color. Quickly pour the caramel into the prepared cake pan, tilting to coat the bottom evenly.

In a blender, combine the evaporated milk, sweetened condensed milk, eggs, and vanilla extract. Blend until smooth and set aside.

In a separate bowl, whisk together the flour, cocoa powder, baking powder, and salt. Gradually add this dry mixture to the blender with the milk mixture, blending until just combined.

Pour the chocolate batter over the caramel in the cake pan. Then, carefully pour the milk mixture on top of the chocolate batter.

Place the cake pan in a larger baking dish and fill the larger dish with hot water until it reaches halfway up the sides of the cake pan.

Bake for 50-60 minutes, or until a toothpick inserted in the center comes out clean.

Remove from the oven and let it cool for about 15 minutes. Carefully invert the cake onto a serving plate. Allow it to cool completely before slicing.