Whisk the eggs in a large bowl. Blend in sugar and beat until mixture is thick and pale, about 10 minutes. Mix in the melted butter and salt. Gradually fold in the flour and lemon zest. Cover and refrigerate for at least one hour or, preferably, overnight.
Preheat oven to 325 degrees F (165 degrees C). Lightly grease cookie sheet.
On a floured surface, roll out dough to 1/4 inch thickness. Cut into desired shapes using cookie cutters. Place cookies on prepared cookie sheet. Brush with beaten egg yolks and decorate with sprinkles.
Bake in preheated oven until golden at the edges, 15 to 20 minutes. Cool cookies on racks.
