• Adjust oven rack to lower-middle position; heat oven to 400℉.
• While the oven is preheating, crack your eggs into your blender pitcher to allow them to warm up. Also, pop your milk in the microwave for about 30 seconds until it's lukewarm, and you can go ahead and melt the butter now too.
• When the oven gets to the proper temperature, place your ungreased muffin tin in the oven for five minutes.
• While the muffin tin is heating, whirl the eggs in the blender until they're a pale yellow color, Add your milk and puree again to combine.
• Now add the flour, salt, and 3 tablespoons of melted butter to the blender, and mix until thoroughly combined and frothy.
• After five minutes have passed, remove the muffin tin from the oven and quickly grease each cup and the top of the tin with the additional melted butter.
• Give the blender a quick pulse to ensure the batter hasn't settled and fill each cup about ⅔ full.
• Bake for 30 minutes at 400℉ — NO PEEKING! This is very important. Do not open the oven door until 30 minutes have passed, or your popovers may collapse.
• Remove from the oven and immediately turn out onto a clean towel or cooling rack. If the popovers are to be served later, prick the side of each with a fork to allow the steam to escape and prevent them from becoming mushy.

For the cinnamon-sugar topping:

• Combine the cinnamon and sugar in a bowl. Melt the butter in a separate bowl.
• Brush each popover top with melted butter, then dredge in the cinnamon-sugar mixture.