Adjust oven rack to center position. Preheat oven to 350 degrees F. Spray a 9-inch springform pan with non-stick cooking spray.
In medium mixing bowl, whisk together white rice flour, sweet rice flour, potato starch, caraway seeds, baking powder, salt, baking soda, and xanthan gum. Set aside.
In bowl of stand mixer, cream together butter and granulated sugar on medium-high speed until a thick paste forms, about 30 seconds. Add eggs, one at a time, until light and fluffy, about 1 minute. Stop mixer and scrape down sides and bottom of bowl.
Add half the dry ingredients. Turn mixer on to low speed. Mix until incorporated, about 20 seconds.
Add half the buttermilk. Mix until thoroughly combined. Repeat with remaining dry ingredients and buttermilk. After adding buttermilk, mix until batter is thick and fluffy, about 45 seconds. Add raisins, mix until incorporated.
Spread batter evenly into prepared pan. Bake bread until golden brown, about 80 minutes. A cake tester inserted into the center of the bread should come out clean.
Allow bread to cool in the pan for 10 minutes. Unmold bread and place on a wire rack to cool completely. Store on the counter for up to two days or freeze for up to two months.