Start by making the pastry dough. Add the flour and salt to a large bowl and slightly whisk. Cut the butter in pieces and add to the bowl. Using a pastry blender or two knives cut but butter in until the mixture resembles coarse meal. In a small bowl, whisk together the sour cream, lemon juice and water and add this to the butter-flour mixture. Using a wooden spoon or your fingers, mix in the liquid until large lumps form. Pat the lumps into a ball; do not overwork the dough. Cover with plastic wrap and refrigerate for 1 hour.
In a bowl toss the peaches, blueberries and sugar together.
Preheat oven to 400 F degrees. Line a baking sheet with parchment paper.
On a floured work surface, roll the dough out into a 12-14 inch round. Transfer to prepared baking sheet.
Arrange the peaches over the dough, leaving a 2-inch border. Fold the border over the filling, pleating the edge to make it fit. The center will be open. Brush crust with egg yolk. Sprinkle with some more sugar if preferred and sprinkle some almonds over the crust.
Bake for about 45 minutes or until golden brown.