Preheat oven to 375 degrees.

Using a microwave or stovetop, melt the butter. Coat the popover pan generously with melted butter. Place pan in the oven to heat it up while the oven finishes preheating.

In a large bowl, whisk together eggs and milk.

Using a separate bowl combine the dry ingredients: flour, sugar, salt, and lemon zest. Add these the egg mixture and stir until just combined. It's okay if it's a little lumpy.

Pour the batter into the prepared pan, filling each cup to about 2/3 full. Scatter a few raspberries over the tops of each cup or mash the raspberries and fold a spoonful into the mixture of each cup.

Bake until puffed and golden, about 35-45 minutes. Sprinkle with powdered sugar and serve immediately, popovers will deflate slightly as they cool.