In a mixer, start by beating together room-temperature butter, brown sugar, and white sugar until everything is light and fluffy. Mix in the freshly grated lemon and orange zest, one egg and vanilla.
Sift flour, baking powder and salt. Mix well then stir into butter mixture until well combined.
Divide dough into 3, wrap in plastic wrap and chill. inthe fridge for one hour or overnight.
Once the dough is chilled, roll it out to about a quarter-inch thickness. Use the plastic wrap with the rolling pin to keep the dough smooth and easy to work with. If it’s being stubborn, gently rock the rolling pin from side to side to help it come together.
Cut out the snowflakes with your favourite cookie cutters and repeat until all the dough is used up. If the dough gets too soft, just pop it back into the fridge for a few minutes.
Bake at 350°F for 10–12 minutes, or until the edges are just slightly golden. Let them cool completely before icing.