For the lemon cookies, mix the flour, baking powder, baking soda and salt in a bowl.
In a bowl, beat the butter with sugar until fluffy and stir in the egg.
Stir in the sour cream, lemon zest and juice. Add the flour mixture and mix until smooth.
Wrap the dough in plastic wrap and chill in the refrigerator for about 2 hours. Preheat the oven to 190 degrees and line two baking sheets with baking paper.
Roll out the dough and cut out cookies with a mold. Place the cookies on the baking sheet and brush lightly with zirton juice.
Sprinkle with sugar and then bake the lemon cookies for 12 to 14 minutes.