Preheat a 12-cup muffin tin for 5 minutes. This is a very important step for popovers. A warm muffin tin helps to facilitate the rising of the batter. Let the tin stay in the oven until you are ready to pour the batter.
In a blender, add eggs and milk and pulse just until blended. Then add the tapioca flour, rice flour and salt and pulse until combined.
Remove your baking tin (remember, it will be hot.) Lightly grease with cooking spray. Pour in the batter, filling each muffin cup 3/4 full. Fill any empty muffin cups with water to ensure even baking.
Bake 25 minutes, or until popovers are puffed high and are a rich, golden brown. For puffiest popovers, avoid opening the oven door before 25 minutes. Serve immediately.
GARLIC & HERB POPOVERS: Mix in after salt: 2 tablespoons fresh herbs (such as rosemary, basil, thyme, sage or a combination), stemmed and chopped fine, and 1 clove minced garlic.
PARMESAN CHEESE POPOVERS: Mix in after salt: 1/4 cup finely grated Parmesan cheese and 1 tablespoon finely chopped Italian parsley.
YORKSHIRE PUDDING POPOVERS: Add 1 tablespoon of meat dripping to bottom of muffin cups.