Preheat oven to 350° F.

In a bowl, whisk together the flour, baking powder, salt, and poppy seeds.

In the bowl of a standing mixer (or using an electric mixer) cream together the butter and sugar for 3 minutes on medium to high speed, or until light and fluffy.

Add the egg, vanilla, and lemon zest and beat until just incorporated.

Turn the speed to low and slowly add the flour mixture until the dough comes together.

Using a lightly floured rolling pin, roll out the dough onto a lightly floured surface until 1/4" thick and even.

Use cookie cutters to cut out desired shapes (I like to start at one end of the dough and make the cuts close together to utilize all of the dough).

Using a spatula, transfer the cut-outs onto a Silpat or parchment-lined cookie sheet.

Bake for 15 minutes, rotating the tray from back to front halfway through cooking until the edges just turn golden.

Cool cookies on a rack.

To make the icing, stir together the lemon juice and powdered sugar until smooth and ice the cooled cookies.