Make the pastry: In a large bowl, mix together the flour, salt and sugar. Add cold butter and use your fingertips to rub it into the dry ingredients until the mixture resembles breadcrumbs. Add enough of the water to create a workable dough. Transfer the dough to your work surface and shape it into a ball. Roll it out between two sheets of baking paper to make a rectangle about 30 x 40 cm that's approximately 5mm thick. Trim the uneven edges to create a smooth border all around. Set aside on a baking tray.

Prep the filling: On a chopping board, slice the peaches and nectarines into thin, 2mm slices. Halve the cherries and remove the pits. Add the raspberries to the chopping board. In a small bowl, combine the brown sugar and cinnamon. Sprinkle half of this mixture over the fruit, along with the juice of half a lemon. Set the remaining sugar mix aside. Using your fingers, gently toss the fruit with the lemon and sugar mixture to coat.

Fill/decorate the galette: Heat the oven to 190°C. Remove the top layer of baking paper then sprinkle a tablespoon of flour over the rectangle of dough. This will absorb some of the moisture from the fruit, preventing a soggy base. Leave a 2-3 cm border around the edges of the dough. Arrange the cherries in a semi-circle, round part up, at the bottom centre of the rectangle. Next, follow the shape of the semi-circle by placing raspberries above the cherries, ensuring there are no gaps. Repeat this process, overlapping the peaches, followed by the nectarines, making sure the entire surface is covered without any gaps. Lift the edges of the dough and fold them over the fruit, pinching the corners together to create a frame around the fruit.

Brush the pastry with beaten egg and sprinkle the remaining sugar and cinnamon over the pastry and fruit. Bake for 40 minutes until the pastry is golden brown and the fruit is soft. Cover with foil if it starts to burn. Remove the galette from the oven and let it cool completely. Dilute the jam with a teaspoon of water to create a glaze and brush it over the fruit. Cut the galette into long strips so each piece includes all the fruits. Serve with a scoop of vanilla ice cream.