Preheat the oven to 350F. Grease a baking sheet with butter.
Grate or shred the almond paste on a flat surface.
Spread over it the baking powder and the flour. Add the lemon zest.
Put the egg whites in a bowl and with a hand mixer whip them until glossy and soft peaks form.
While whipping add the sugar.
Fold into the egg whites the almond paste and mix well.
Whip the entire content with a hand mixer for 2 mins.
Take a greased cookie sheet and with a small ice cream scoop take a lump of the mix, drop it in the pignoli nuts and then transfer the ball on the cookie sheet.
At the end add some pignoli nuts in the spots that were missed.
Bake the cookies for 15-20 minutes.