Preheat the oven to 375° F. Grease an 8 to 9-inch round cake pan and dust with sorghum flour.

In a glass measuring cup, place the vinegar. Add enough milk to measure 1 cup. Let stand 5 minutes to thicken (this makes instant buttermilk, 1 cup buttermilk can replace the vinegar and milk mixture). Add the egg and whisk to blend.

In the bowl of a food processor, combine the oat flour, sorghum flour, potato starch, brown sugar, xanthan gum, baking powder, baking soda, and salt. Process to blend. Add the butter and cut in until the mixture resembles a fine meal. Add the oat bran and flaxseed and blend in.

Transfer the mixture to a medium bowl. Mix in the sunflower seeds. Add the liquid ingredients. Using a silicone or rubber spatula, mix until a sticky batter forms. Scrape the batter into the prepared pan. Dip the silicone spatula into water and use to form the dough into a smooth round loaf. Flatten slightly. Using a serrated knife, cut a ¼-inch deep cross into the top of the loaf, cutting to the edges. Sprinkle the loaf with chia seeds.

Place the bread in the oven and bake until it browns slightly, sounds hollow when tapped, and a tester inserted into the center comes out clean, about 50 minutes. Cool in the pan on a wire rack 5 minutes Transfer the loaf to a wire rack and cool. Serve warm or at room temperature. Store airtight up to 2 days.

Tips: An interesting note on sunflower seeds: They are rich in a healthful antioxidant, but it can occasionally turn the seeds green when baked. This is harmless, and makes this bread a good candidate to serve on St Patrick’s Day. Mine didn’t turn green until a day or two after baking. To avoid this, replace the sunflower seeds with pumpkin seeds, any nut you like, or raisins.

If you don’t have both oat bran and flax seed meal, use 5 tablespoons total of whichever is in your cupboard