Cream softened butter in a bowl until smooth, then add sugar and mix until fluffy.

Gradually add beaten egg while mixing, then add vanilla extract and combine well.

Sift cake flour and baking powder into the mixture.

Mix gently with a spatula until just combined and no dry flour is visible.

Roll the dough between parchment paper to 3mm thickness (approximately 28×28cm). Chill in the refrigerator for 30 minutes to 1 hour if needed.

Mix brown sugar and cinnamon powder in a bowl.

Spread the filling evenly over the dough, leaving a 1–2cm border. Roll the dough tightly into a log.

Place the rolled dough into a kitchen towel core for shape retention and freeze for 1 hour.

Let the dough sit at room temperature for 5 minutes before slicing into 5–7mm thick pieces.