Preheat the oven at 375°F (190°C) and line a baking sheet with parchment paper.
Beat the butter and sugar together until fluffy, about 2 min. Add in the egg and vanilla extract, mix. Then stir in the flours, cardamom, and zest until the dough comes together.
Roll the dough out on a floured work surface, about ½ in (1 cm) thick. Cut with cookie cutters or a knife if you’re in a hurry.
Bake for 8 to 10 min. Set aside to cool and harden for 5 min before eating.
You can use 100% all-purpose flour if you don’t have buckwheat flour, or replace buckwheat with whole wheat flour. Try a variation: ¼ cup (30 g) of poppy seeds and the zest of 3 lemons (Meyer if possible) instead of the cardamom and orange zest.