01 -
Set your oven rack to middle height and warm it to 450°F. Put your 9- or 10-inch cast iron pan on the stove at low heat and keep it warming while you mix everything else.
02 -
Melt two tablespoons of butter in a little pan, then pour it into your blender. Throw in the milk, flour, eggs, white sugar, vanilla, salt, and lemon zest, then blend until it's smooth. Don't try to mix by hand or you'll get lumps.
03 -
Drop the other 2 tablespoons of butter into your warm cast iron pan and crank the heat to medium-high. Once the butter's melted, toss in your blueberries and gently shake the pan around.
04 -
Right away, pour your smooth batter over the warm blueberries and stick the whole pan in the oven. Let it cook until it puffs up and turns golden brown, about 15 minutes.
05 -
Take your pan out of the oven, sprinkle some powdered sugar on top if you want, cut it into pieces, and serve it right away with some maple syrup.