In a food processor, pulse together rice flour, salt, shortening, brown sugar and butter.
Mix together the water and lemon juice and add 1 tbsp of this at a time to the mixture until dough forms.
Form dough into a ball, wrap, and chill in refrigerator for one hour.
To roll out dough, place between 2 sheets of wax paper. Roll out to a 12-inch circle and place onto a parchment lined baking sheet.
For the filling, toss peaches and cornstarch with sugar.
Place mixture into pastry, leaving 2" open around the edges, then fold pastry edges over fruit. This is supposed to look rustic, so rough and uneven edges are what you want.
Brush pastry with cream, sprinkle with sugar, then bake at 425°F 25-30 minutes, until pastry is golden brown.