Preheat your oven to 375°F (190°C). Line a baking sheet with parchment paper.
In a large bowl, whisk together the almond flour, psyllium husk powder, coconut flour, baking powder, and salt until evenly combined.
Add the eggs and melted butter to the dry mixture and stir well. Pour in the hot water and mix quickly until a firm, slightly sticky dough forms. Let it rest for 2 minutes so the psyllium husk fully absorbs the moisture.
Divide the dough into 6 equal pieces. Roll each piece into a log shape about 5 inches long and 1.5 inches wide, roughly the size of a standard hot dog bun. Place them on the prepared baking sheet, spaced about 2 inches apart.Flatten the tops just slightly with damp fingers and sprinkle sesame seeds over each bun.
Bake for 22 to 28 minutes, until the buns are golden brown all over and feel firm when pressed. They should sound slightly hollow when tapped on the bottom.
Transfer to a wire rack and let them cool completely. Once cooled, slice each bun lengthwise along the top, cutting about three-quarters of the way through so the bun hinges open.
For the best results, lightly toast the inside of each bun in a dry skillet over medium heat for about 30 seconds before loading it with a hot dog and your favorite toppings.