1. To make the pastry,sift together the flour,icing sugar and salt and place in a food processor. Add the butter and lemon zest,then pulse a few times until the mixture is the consistency of fresh breadcrumbs.
2. Lightly whisk together the egg yolk with the ice-cold water. Add this to the mix,pulsing just to combine. Tip the dough out onto a lightly floured bench,and dusting your hands lightly with flour,pat gently to bring together. Divide the pastry into two,wrap each half loosely in cling film and press gently to form flattish discs.
3. Chill in the fridge for at least an hour (and up to 3 days) before using. (Use only one disc for this tart;freeze the other for another time.)
4. To make the filling,place the butter,sugar and lemon zest in the bowl of a stand mixer fitted with the paddle attachment,and beat until lightened. Add the eggs,one at a time,beating well after each addition.
5. Sift the flour,baking powder and salt together into a small bowl,then add the ground almonds and pistachios. With the mixer on low speed,add the dry ingredients to the butter and sugar mix,beating just until everything is combined. Finally,fold in the almond extract.
6. To make the tart case,remove the cling wrap from one of the pastry discs and roll out on a lightly floured bench to about 4mm thickness. Line the tart tin with the pastry,allowing an overhang of about 2cm. Place in the fridge to rest and chill for at least 30 minutes.
7. Preheat the oven to 200C (180C fan-forced). Line the chilled pastry case with a sheet of parchment paper and fill with baking beans. Place in the oven and blind bake for 20 minutes,then scoop out the baking beans,lift off the paper and return the tart to the oven. Immediately reduce the temperature to 190C (170C fan-forced) and bake for a further 7 minutes,or until a light golden brown. Remove from the oven but leave the oven on at the same temperature.
8. Allow the pastry case to cool for 5 minutes,then use a small paring knife to trim off the overhanging pastry. Spread the jam over the base,then dollop spoonfuls of the nut filling on top. Using a small spatula or the back of a spoon,smooth the filling evenly over the entire surface. Place the cut fruit on top,then sprinkle over the nuts.
9. Place the tart in the preheated oven and bake for about 40 minutes,until the filling is set.
10. Allow the tart to cool in the tin before easing it out and onto a serving plate.