Put butter into freezer 15 minutes ahead of time. In a large bowl, mix together flour, sugar and salt. Using a pastry cutter or two forks, cut in the butter until the mixture resembles pea-sized crumbs. Drizzle water over the dough and bring together (add 1 more tablespoon of water if dough seems dry.) Gently knead the dough a few times in the bowl until it all comes together. It is important not to handle the dough too much. Flatten the dough into a disk, wrap tightly in plastic wrap and cool in the refrigerator for 1 hour.
Preheat oven to 190°C (375°F). Line a large baking sheet with parchment paper or a silicone baking mat. Set aside.
Place the butter and the sugar and using an electric mixer cream together. Add the almond meal and mix to combine.Then add the egg and vanilla, gently beating until all is mixed. Add the flour and whisk until fully incorporated.
Mix the apples and pears, brown sugar, flour, lemon juice, cinnamon, and nutmeg together in a large bowl. Cover tightly and let sit until the dough is ready.
On a lightly floured surface, roll out the dough into a approx 30 cm (12 inch) circle that is about 3 mm thick. Transfer dough to the prepared baking sheet.
Evenly spread the frangipane into the center of the dough, leaving a 5 cm (2 inch) inch edge.Arrange the apples and pears (but not the juices) over the frangipane filling.Gently fold the edges of the dough over the filling, overlapping the dough as necessary. Brush the egg wash over the crust and sprinkle with sliced almonds.
Bake until the filling is bubbly and the crust is golden brown, about 30-35 minutes. Cool on the baking sheet for 10 minutes before slicing and serving. Tastes wonderful served warm with vanilla ice cream.
I always suggest using a kitchen scale. If you don't have one, buy it! They are cheap and you will always ensure same results in baking!