Mix butter and powdered sugar until light and smooth.

Add egg yolks, vanilla, and lemon zest. Mix well.

Mix cornstarch, flour, baking powder, and salt in a bowl.

Add to wet mixture and mix until dough forms. Do not overmix.

Wrap dough and chill for 30–60 minutes.

Roll to about 5 mm thickness.

Cut into 4–5 cm circles.

Bake at 160°C for 8–10 minutes. Keep them pale.

Let cookies cool completely before filling.

Spread dulce de leche on one cookie and sandwich.

Roll edges in coconut or dust with powdered sugar.