Preheat the oven to 200°C.
In a bowl, mix cake flour, baking powder, and salt.
Add cold butter and cut it into small pieces using a scraper.
Add milk, erythritol, and egg whites, then knead the dough.
Roll the dough out to 2cm thickness and cut into triangles.
Place the scones on a baking tray lined with parchment paper.
Bake at 180°C for 18 minutes.