Remove the chilled tart from the fridge.
With an offset spatula or the back of a spoon, spread 1/2 cup of apricot jam over the pastry dough.
Starting at the outer edges of the tart, place one row of sliced peaches (skin side up) in a circular pattern. Do not overlap.
Place the chilled pastry dough cutouts in an upright position and overlapping, alongside the peach slices, also forming a circular pattern.
Repeat 2 more times until you have approximately 1 inch round space remaining in the middle.
Fill this space with thinly sliced peaches while overlapping the thin slices in a circular pattern and the centre is completely filled.
Warm a tablespoon of apricot jam in the microwave and gently brush the jam over the peaches.
Sprinkle the top with demerara sugar.
Bake the crostata in a preheated oven at 350 degrees F, for about 35 minutes.
Transfer to a wire rack and brush with another tablespoon of warm jam.
Allow to cool, then dust with powdered sugar before slicing and serving.