Preheat oven to 400°F. Coat loaf pan or 9-inch-square baking pan with cooking spray. Whisk together cornmeal, rice flour, potato starch, baking powder, baking soda, and salt in bowl. Stir in sage. Beat egg in separate bowl. Whisk in buttermilk and honey. Stir wet mixture into dry mixture. Let stand 5 minutes. Spread batter in prepared pan, and bake 20 to 35 minutes, or until crisp and brown on top and sides. Brush with butter, if using. Cool 15 minutes before slicing.