For the pastry put the flour, icing sugar and butter into a food processor. Blend until it resembles breadcrumbs. Add the egg and mix until the mixture holds together. Tip onto a floured work surface and gather the dough into a ball. Wrap in cling film and chill in the fridge for approximately 15 minutes.
Preheat the oven to 200C/400F/Gas 6 and place a baking tray on the middle shelf to heat. Line the base and sides of a 23cm/9in round deep fluted tin.
Take two-thirds of the chilled pastry from the fridge. Roll it out thinly to make a circle large enough to line the base and sides of the tin. Use a rolling pin to lift the pastry into the tin.
Use a small ball of excess pastry to press the rolled out pastry into the base and sides of the fluted tin (this will help prevent holes forming in the pastry). Ensure the tin is fully lined, with no holes.
Coarsely grate or finely chop the almond paste or marzipan and sprinkle it over the base of the tart
Drain the apricots thoroughly and pat dry with kitchen paper. Arrange the apricots over the base of the tart cut side down.
Roll out the remaining pastry to form the lid. Dampen the edge of the pastry base in the tin. Lift the pastry lid over the top of the fruit and press the two layers of pastry together around the edge of the tin, patching the edges if necessary.
Place the tart on the preheated baking tray and bake in the centre of the oven for approximately 30-35 minutes, or until pale golden-brown.
To serve, dust with icing sugar and serve with crÃ¨me fraÃ®che or cream.