Pre-heat oven to 180C
Place nuts in a food processor and process until medium fine in texture.
Line baking sheets with parchment paper and set aside until ready to use.
Beat butter and sugar together with an electric mixer on a medium high until light and creamy in texture.
Add eggs and beat until smooth.
Add vanilla and beat until combined.
In a separate bowl, combine flour, nuts, baking powder, cinnamon, salt, and lemon zest.
Add the flour mixture to the butter mixture and beat to combine.
Place in freezer until firm, approximately 30 – 40 minutes.
Dust a clean surface generously with flour, and roll out the dough to approximately 1/8-inch thickness.
Using the linzer cutter without an insert, cut out cookies (at least 36) and transfer to the prepared cookie sheets – these will be the bottom pieces
Next cut out 36 more with an insert shape in cookie cutters – these will be the top pieces of the cookies. You can either re-roll the cutouts or bake them.
Bake all cookies for about 8 minutes until golden brown. Transfer to a wire rack until completely cooled.
Sift confectioners sugar over top pieces of the cookies.
Spread about 1 teaspoon jam on each of the bottom halves and place top half (cut out piece) on jam covered bottom half.
Cookies can be stored carefully in an airtight container for up to one week.