Cinnamon Swirl
In a medium bowl, stir together the butter, sweeteners, and cinnamon. The butter should be almost melted but not quite, and the mixture should be like a thin paste. Set aside.
Muffins
Preheat the oven to 325ºF and line the wells of two muffin pans with silicone or parchment liners. If you only have one pan, you may need to work in batches.
In a blender, combine the cottage cheese, eggs, sweetener, and vanilla, and blend until smooth. Add the almond flour, whey protein, baking powder, and salt and blend again until smooth.
Fill each muffin cup about half full with the batter. Then add half a teaspoon of the cinnamon swirl into the center of each muffin and swirl lightly with a toothpick or the end of a small spoon. Take care not to push the cinnamon mixture toward the bottom of the muffin.
Divide the remaining batter overtop, then add more cinnamon swirl and swirl it in.
Bake 15 to 20 minutes, until the muffins are puffed and golden brown. The very top may not seem cooked through because of the buttery cinnamon mixture, but it will set when they cool.
Remove and let cool 20 minutes, then transfer to a wire rack to cool completely.
Optional Drizzle
In a small bowl, whisk together the sweetener and heavy whipping cream. Add water in tiny amounts until a drizzling consistency is achieved. Drizzle over the cooled muffins.