For the pastry, sift the flour and
salt into a bowl. Add the butter and margarine and rub in until the
mixture resembles coarse breadcrumbs. Stir in just enough water to bind
the dough. Wrap and chill for 20 minutes. Roll out the pastry to a 5mm
thickness. Use to line a 20cm tart tin. Trim and chill until needed.
In a saucepan, combine 165g of the
sugar and the orange juice and boil until thick and syrupy. Cut the
unpeeled oranges into 5mm slices. Add to the syrup. Place a baking sheet
in the oven and heat to 200oC/400oF/Gas 6.
Grind the almonds finely in a blender
or food processor. Cream the butter and remaining sugar until light and
fluffy. Beat in the egg and 30ml of the orange syrup. Stir in the
almonds and flour.
Melt the jam over a low heat, then
brush over the pastry case. Pour in the almond mixture. Bake on the
baking sheet until set, about 20 minutes, then cool. Arrange overlapping
orange slices on top. Boil the remaining syrup until thick and brush on
top to glaze.