Preheat the oven to 175 ° C top / bottom heat. Line 2 - 3 trays with baking paper.
Mix the butter with sugar and salt until frothy. Stir in the egg yolk and lemon zest. Mix the flour and breadcrumbs and add.
Shape the dough into balls the size of a hazelnut and distribute them on the baking sheets. Make small indentations in the balls with the handle of a wooden spoon or a glass tube with aromatic oil. Pour the jam into a small freezer bag, cut off a tiny point and fill the indentations with it.
Bake the biscuits on the trays for 10-15 minutes, one after the other, until the edge of the biscuit begins to brown slightly.
Place the finished biscuits on a wire rack with the baking paper and let them cool. Dust with powdered sugar.
Store separately in layers in a tin can with (baking) paper.