Rub the butter with the raw cane sugar with the tip of your fingers.
Mix in the beaten egg. Sift the spelt flour with salt, then rub it into the dough.
Knead into a ball, flatten it a little bit, wrap in cling film and let it rest in the fridge while you're making the filling.
Heat oven to 180°C.
Peel the nectarines, dice them and simmer in a saucepan with raw cane sugar, lemon zest and lavender. Simmer for about ten minutes over low heat, until soft and almost melting.
Remove the pastry from the fridge and roll out on a floured surface with a rolling pin.
Butter and flour 8 10cm wide tartlet moulds and line them with the pastry dough, spoon the peaches into the pastry cases and decorate with a lattice top.
Bake the tartlets for about 25 minutes, until golden brown.