Preheat the oven to 350 degrees F (177 degrees C). Lightly grease a 9-inch (22 cm) springform pan.
In a large mixing bowl, whisk together 1 cup sugar and oil until well combined. Whisk in the sour cream, eggs, and vanilla.
In a separate bowl, whisk together the rice flour, sorghum flour, potato starch, tapioca starch, baking powder, xanthan gum, baking soda, cinnamon, and salt.
Stir the dry ingredients into the wet ingredients, just until incorporated.
Dust the blueberries and peaches with the 2 tablespoons rice flour. Stir until the fruit is coated with the flour. This will prevent the fruit from sinking to the bottom of the cake.
Gently fold the blueberries and peaches into the batter. Scrape into the prepared baking pan.
In a small bowl, combine the sorghum flour, rice flour, sugars, and cinnamon. Stir in the butter, until the mixture resembles wet sand. Some small pieces of butter is alright. Stir in the pecans, and sprinkle the topping mixture over the top of the cake.
Bake in the preheated oven for 62-67 minutes, or until a toothpick inserted into the middle of the cake comes out clean.
Cool on wire cooling rack, then carefully cut around the outside of the cake, releasing the cake from the pan. Remove the springform collar and cool cake completely before storing in an air-tight container in the fridge.
You can mix up a glaze by mixing 1/2 cup confectioners' (icing) sugar with 2 to 3 tablespoons of milk or cream. Drizzle it on after the cake has cooled. I've made this cake both ways, and actual prefer it without the glaze.
Recipe by Faithfully Gluten Free at http://www.faithfullyglutenfree.com/2014/07/gluten-free-blueberry-peach-coffee-cake.html