Preheat the oven to 350℉. Generously grease the inside of a bundt pan with 1 tablespoon of softened butter. Pour the cajeta in to coat the bottom and set aside.

In the bowl of a stand mixer using the paddle attachment or in a large bowl using an electric hand mixer, beat together the sugar and remaining 4 tablespoons of softened butter until creamed.

In a separate medium bowl, mix together the flour, cocoa powder, baking soda and salt.

Add the flour mixture to the creamed butter and sugar and mix until combined.

Add the milk, 1 egg, and vinegar. Mix for another 40-60 seconds until completely smooth.

In a large blender, add the evaporated milk, sweetened condensed milk, cream cheese, the remaining 3 eggs, and vanilla extract. Blend on high for 30 seconds.

Pour the cake batter into the prepared bundt pan and spread it evenly. Then, slowly and gently pour the blended flan mixture over the cake batter. It's okay if the cake batter and flan mixture combine a bit. They will invert during baking anyway!

Carefully place the roasting pan in the center rack of the oven and bake for 1 hour and 25 to 1 hour and 40 minutes or until the surface of the cake is firm to the touch and a toothpick inserted into the cake comes out clean.

Slide a knife along the edges of the cake pan to unstick any pieces, then place a large plate or cake stand over the bundt pan. Grasp both of them tightly, give it a little jiggle, then flip it over. The chocoflan should slide right out.

Remove the pan and scrape any remaining cajeta from the pan onto the cake. Garnish with sliced almonds or chopped pecans and serve.