Mix all the avocado sauce ingredients in a blender or food processor. Blend until smooth. Set aside in the fridge until ready to use, covering with plastic in a way that the plastic touches the surface of the sauce.
In a large bowl, mix the masarepa, salt, butter, milk, and water. Stir to fully combine. Continue to stir for a few minutes, then allow to rest for 5 minutes before using.
Preheat a cast iron pan to high heat
spread out a little masarepa on a plate and dip the hot dog in it.
Pick up some of the arepa dough and flatten it on a piece of parchment paper. Place the hot dog in the middle and wrap the dough around 3/4 of the dog, leaving the top exposed. Remove excess dough, you only want a thin layer. Flatten the 4 edges of the arepa dough so that it can cook and char evenly in the pan, and so that the hot dog is equal or higher than the top edges.
Add the arepa to the dry pan and repeat with remaining dogs. Flip the dogs in the pan every few minutes to char evenly on all sides.
Serve the dogs with the sauce on the side.