Spray a 9-inch x 5-inch bread pan or 9-inch x 4-inch small Pullman loaf pan with gluten-free cooking spray. Move the top oven rack to the middle rack. Preheat your oven to 350°F. I used both a 9-inch x 4-inch Small Pullman loaf pan.
Add the gluten-free flour, baking powder, and instant yeast to a large bowl and stir to combine the ingredients.
Add the olive oil, honey, and apple cider vinegar, and warm water to the flour mixture and mix on low for 1 minute. If you are using a stand-up mixer use the paddle attachment, not the dough hook.
Add the egg whites and the salt to the dough and mix on medium for 1 minute. The dough will look like a thick cake batter.
Pour the dough into a greased 9-inch x 5-inch bread pan or the 9-inch x 4-inch small Pullman loaf pan. I HIGHLY recommend using a 9-inch x 4-inch Small Pullman loaf pan (linked in Notes below). Spray plastic wrap with gluten-free cooking spray and cover the top of the pan. Cover the pan with a kitchen towel and allow the bread to rise in a warm place to rise for 30 minutes.
Place in the oven to bake for 30 minutes at 350°F. Bake the bread on the middle rack horizontally. The bread will be golden brown and have the internal temperature between 205-210ºF.
Allow the loaf to cool for 10 minutes in the pan. Remove the loaf from the baking pan and place it on a cooling rack. If the bread completely cools in the pan, the steam can get trapped and the loaf can get soggy, especially on the bottom. Allow the bread to cool completely before slicing.