Evenly butter a mould (26 cm wide) wash the apricots, cut them in half and remove the stone. Melt the butter in a pan, add the sugar and rosemary leaves, put the apricots with the round part on the bottom and cook them 10 or 15 minutes to candy them Slide the contents of the pan into the mould and let it cool down. Attention - this is the most important step to have a great tarte tatin!!!
Heat the oven at 210°C. Prick the pastry with holes and lay it on the apricots. Carefully tie the pastry to the border of the mould. Turn down the oven temperature to 180°C and bake for 30 minutes.
Let the cake cool down 5 minutes then turn the tarte tatin upside down on the serving dish.
A suggestion - serve it with cream ice-cream!!