Preheat the oven to 325°F. Grease a 9x5-inch loaf pan and line it with parchment paper.
Blend the cottage cheese until completely smooth and set it aside.
Beat the softened butter and sweetener for 2 to 3 minutes until light and fluffy. Add the eggs one at a time, beating well after each one.
Mix in the blended cottage cheese and vanilla until smooth. The batter may look slightly curdled at this point, which is normal.
In another bowl, whisk the almond flour, coconut flour, baking powder and salt. Add to the wet mixture and mix on low just until combined and thick.
Spread the batter into the pan and smooth the top. Bake for 60 to 70 minutes, until deep golden and a toothpick comes out clean, covering with foil after 35 minutes if needed.
Cool in the pan for 20 minutes, then move to a wire rack and cool completely before slicing. The crumb gets even better and more buttery the next day.