Prep the pan and oven: Preheat your oven to 350°F (175°C). Line a 10x15-inch jelly roll pan with parchment paper, leaving overhang on two sides to lift the cake out. Lightly grease the parchment.

Separate and whip the eggs: Crack 5 large eggs, placing whites in one bowl and yolks in another. Whip the whites with a pinch of salt until stiff peaks form. This gives the sponge its lift and soft texture.

Make the yolk mixture: In the yolk bowl, whisk 1/3 cup granulated keto sweetener, 1 teaspoon vanilla, 1 tablespoon lemon zest, and 1 tablespoon lemon juice until pale. Add 1 tablespoon melted butter (optional) and whisk smooth.

Combine dry ingredients: In a small bowl, whisk 1 cup almond flour, 1 tablespoon coconut flour, 1 teaspoon baking powder, and a small pinch of salt.

Fold the batter: Stir the dry ingredients into the yolk mixture. The batter will be thick. Gently fold in one-third of the egg whites to loosen, then fold in the remaining whites in two additions. Keep a light hand to avoid deflating.

Spread and bake: Pour the batter into the prepared pan and spread evenly to the edges. Bake for 10–12 minutes, or until the top is set, lightly golden, and springs back when touched. Do not overbake.

Roll while warm: Lay a clean sheet of parchment on the counter and dust it with a little powdered keto sweetener. Invert the hot cake onto the parchment and peel off the baking paper. Starting from a short side, roll the cake up with the parchment inside. Let it cool completely in this rolled shape.

Make the lemon filling: Beat 6 ounces softened cream cheese with 1/3 cup powdered sweetener until smooth. Add 1–2 tablespoons lemon juice, 1 teaspoon lemon zest, and 1/2 teaspoon vanilla. In a separate bowl, whip 3/4 cup heavy cream to stiff peaks, then fold it into the lemon cream cheese until fluffy and spreadable.

Unroll and fill: Carefully unroll the cooled sponge. Spread the lemon cream evenly, leaving a 1/2-inch border at the far edge to prevent overflow.

Roll and chill: Roll the cake back up (without the parchment) as tightly as you can without squeezing out the filling. Wrap in parchment or plastic and chill for at least 1 hour to set.

Finish and serve: Dust with powdered sweetener and garnish with extra lemon zest if you like. Slice with a sharp knife, wiping between cuts for clean layers.