Place the gluten-free flour and caster sugar in a bowl. Cut the butter into cubes and rub into the flour until it resembles breadcrumbs. Make a well in the centre and add the beaten egg and water and stir with a palette knife or spatula to combine. Bring the mixture together into a ball of dough.

Place the pastry between 2 sheets of cling film, roll out into a circle and then fit it into a 23cm loose bottomed flan dish. Chill for 20 minutes in the fridge while you make the frangipane.

Preheat the oven to 190°C/fan 170°C/gas mark 5.

For the filling: beat the butter and sugar together in a large mixing bowl using an electric hand whisk. Gradually add the eggs, beating well after each addition. Add the almond extract, stir in the ground almonds and gluten-free flour.

Spread the jam over the chilled pastry case and then spoon the frangipane on top, spreading it evenly.

Cut the plums in half and remove the stone, slice them down into thin slices and place over the frangipane slightly overlapping each one.

Place in the oven and cook for 30 minutes until the frangipane is set. Allow to cool slightly in the tin before removing onto a serving plate. The tart is best served warm with cream, Greek yogurt or custard.