In a large bowl, mix eggs, sugar, lemon zest, liqueur, baking powder, and butter.
Combine well with a fork. Add the flour a little at a time along with the whole unpeeled almonds. If the dough gets too sticky, do not worry and add some more flour to make it compact.
Transfer the dough on a lightly floured surface and knead it until it gets more compact.
Roll it into long logs (yields about six) and place them on a baking sheet lined with parchment paper.
Bake at 350°F (180°C) for about 30 minutes in a static oven
Remove the baking sheet from the oven.
Let the logs cool for 5 minutes and use a serrated knife to cut them diagonally into ½ inch (1.5 cm) slices.
Put the cantuccini back in a convection oven at 350°F (180°C) and bake for 10 minutes until golden brown.