Preheat the over to Gas 4, 180°C, fan 160°C. Roll out the pastry to a rectangle approx 25cm x 15cm.
Place on a baking sheet and cut half way through the pastry to make a 1cm border.
Cream together the butter and sugar until pale and fluffy, gradually add the egg, stir in the almonds and flour until combined.
Spread the mix over the base of the tart within the border. Top with the apple slices, over-lapping them slightly, brush with the apricot jam to glaze and sprinkle over sugar.
Bake for 20-25 minutes until puffed and golden.
Enjoy hot or cold with coffee and cream for an indulgent treat.
Cooks' tip: Find out more about our British apples