linzer squares thumbprints 1 c hazelnuts,whole unblanched 1 c butter,unsalted,chilled 2 c flour 2/3 c sugar 1 t baking powder 1 t cinnamon,ground 1/4 t salt 2 lg egg,separated 1 t vanilla extract 1 t lemon zest,finely grated 1 c raspberry jam,seedless 1 nut coating,for thumb-prints (opt) 2/3 c hazelnuts,unblanched-chopped finely preheat oven to 350 degrees. for squares, line the bottom and 2 sides of an 8 quot;x8 quot;x2 quot; metal baking pan, with an 8 quot;x16 quot; strip of heavy duty al