First, preheat the oven to 180C or 350F. Meanwhile, line a baking tray with greaseproof paper and set it aside. This step ensures the pastry will not stick and will brown evenly.

Next, add the almond flour, coconut flour, powdered sweetener, and salt to a food processor. Pulse several times until the mixture becomes evenly combined and no lumps remain. This blending step helps create a uniform pastry texture later.

Then, add the softened butter, cream cheese, egg, and vanilla extract. Pulse in short bursts until the mixture comes together into a soft, slightly sticky dough. Avoid over-processing, because excessive mixing can make the pastry greasy and fragile.

After that, transfer the dough onto a sheet of cling film. Shape it into a compact ball, then wrap tightly. Place the wrapped dough in the freezer for 10 to 15 minutes. Chilling the dough firms up the fats, which makes rolling much easier and prevents sticking.

Meanwhile, prepare the raspberry filling. Add the frozen raspberries to a small non-stick saucepan and heat over medium heat. Stir occasionally while the raspberries soften and release their juices. Then, gently mash them with the back of a spoon or spatula until mostly broken down.

Once the raspberries are soft, remove the pan from the heat. Sprinkle the xanthan gum evenly over the mixture while stirring continuously. The filling will thicken gradually as it cools. If desired, add powdered sweetener and stir until dissolved. Allow the filling to cool completely before using, because warm filling will soften the pastry too much.

Next, remove the chilled dough from the freezer. Divide it evenly into two portions. Place one portion between two sheets of greaseproof paper. Roll gently into a rectangle shape about 3 to 4 mm thick. If the edges crack, press them back together gently with your fingers.

Then, trim the edges to create straight sides. Cut the dough into equal rectangles. Repeat the rolling and cutting process with the second portion of dough. Gather any scraps and reroll to create additional rectangles.

After that, arrange half of the rectangles on the prepared baking tray. These will be the bottom layers. Brush lightly with egg wash if using, because this helps seal the edges.

Next, spoon approximately 1 tablespoon of cooled raspberry filling into the center of each bottom rectangle. Spread gently, leaving about 1 cm border around the edges. This space allows proper sealing.

Then, place a second rectangle over each filled piece. Press gently around the edges to seal. Use a fork to crimp the edges securely. Afterward, poke 2 or 3 small holes in the top layer to allow steam to escape during baking.

At this stage, place the tray into the freezer for 10 minutes. This short chilling period helps the pastry hold its shape and prevents breaking while baking.

Next, transfer the tray directly from the freezer to the oven. Bake for 15 to 17 minutes, or until the pastry turns golden brown. Watch carefully during the last few minutes to avoid over-browning.

Once baked, remove the pop tarts from the oven and allow them to cool completely on the tray. The pastry will firm up as it cools, which improves the texture.

Meanwhile, prepare the icing if desired. Add powdered sweetener to a bowl, then add water gradually while stirring. Continue mixing until a smooth, thick icing forms.

Finally, spoon the icing over the cooled pop tarts. Spread gently with the back of a spoon. Allow the icing to set completely before serving.