Preheat the oven to 180°C (356°F).
Mix tomato purée and butter together in a bowl.
Add sugar and egg, and mix well until combined.
Sift in cake flour, baking powder, and salt, then mix to make dough.
Take bite-sized portions of dough and shape them into balls.
Place the dough balls onto a baking tray.
Bake in the preheated oven at 180°C for 12–15 minutes.
Cool on a wire rack.