Preheat the oven to 350°F. Grease four 4-inch ramekins generously with 1 tbsp butter and place them on a baking sheet.
Blend the cottage cheese, eggs, melted butter and apple cider vinegar in a blender until completely smooth.
In a medium bowl, whisk together the almond flour, coconut flour, baking powder and sea salt. Add the blended mixture and stir until a thick batter forms, then let it rest for 3 minutes.
Divide the batter evenly among the ramekins and smooth the tops with the back of a damp spoon.
Bake for 18 to 22 minutes, until the tops are lightly golden and spring back when gently pressed.
Cool in the ramekins for 5 minutes, then run a small spatula around the edges and turn the muffins out. Cool on a wire rack for 10 minutes more.
Split each muffin around the middle with a fork to create those classic nooks, then toast until the edges are crisp and golden.