Preheat the oven to 350°F. Grease an 8-inch round cake pan and line the bottom with parchment paper.
Blend the cottage cheese until smooth. Whisk it with the eggs, melted butter, lemon zest and vanilla until creamy.
In a separate bowl, whisk the almond flour, 2 tablespoons coconut flour, granulated sweetener, baking powder and salt. Add to the wet ingredients and stir until combined.
Toss the blueberries with 1 teaspoon coconut flour so they don't sink. Gently fold two thirds of them into the batter.
Spread the batter into the pan and scatter the remaining blueberries on top.
Bake for 35 to 40 minutes, until golden and a toothpick in the center comes out clean, avoiding the berries.
Cool in the pan for 15 minutes, then transfer to a rack. Dust with powdered sweetener once completely cool and serve.