Knead flour, cold butter, sugar, egg, grated zest of 1⁄2 organic lemon and 1 pinch of salt until smooth. Cut the dough in half and wrap in cling film and chill for about 30 minutes.
Bring the strawberry and apricot jam to the boil in small pots and boil down for about 5 minutes while stirring. Let cool off.
Roll out each portion of dough on a piece of floured baking paper into a rectangle (approx. 18 x 24 cm). Spread with strawberry or apricot jam and roll up using the baking paper. Cut the rolls into slices of approx. 1 cm thickness and place them on baking trays lined with baking paper. Bake one after the other in a hot oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer) for 18-20 minutes. Let them cool down.