From: Art of Gluten-Free Baking (http://artofglutenfreebaking.com)
-adapted from Barefoot Contessa, How Easy is That?, by Ina Garten
Preheat oven to 350 degrees F/180 degrees C/Gas Mark 4. Grease a 9-inch/23 cm square pan with the melted butter.
In a small bowl, mix together flour, baking soda, baking powder, salt, and ½ teaspoon of ground cinnamon.
In another small bowl, mix together ¼ cup of granulated sugar and the remaining 1 teaspoon of cinnamon.
In the bowl of a stand mixer fitted with the paddle attachment, beat the butter and 1 cup of sugar on medium high until light and fluffy—about 2 minutes. Add the eggs, one at a time, beating on low until combined. Beat on medium high until light and fluffy, 1 minute. Add vanilla and sour cream, beating on low until combined.
With the mixer on low, slowly add the flour mixture until well combined.
Spread half of the batter into the pan. The batter is quite thick and this will take a bit of spreading. Top the batter layer with ½ of the sliced peaches. Sprinkle with 2/3 of the sugar-cinnamon mixture. Spread the remaining batter on top of this, arrange the remaining peaches on top, sprinkle with pecans, and then with the remaining sugar-cinnamon mixture.
Bake at 350 degrees F until a tester inserted in the center comes out fairly clean—about 1 hour and 10 minutes.
Remove from oven and let cool in pan on a wire rack. Serve warm or at room temperature.
Store loosely covered, at room temperature, for 1 day. Then store loosely covered in the refrigerator for about 3 days. The fresh peaches in this cake make it prone to spoiling fairly quickly. Also, note that the juice from the peaches will soak into the cake over time, so the cake layers become spongy and peach-infused after about the first day or so.