Preheat your oven to 375°F. Place the butter in a 9-inch cast iron skillet or heavy-bottom 9-inch cake pan.
Place the pan with the butter in the preheated oven just until the butter is melted, while you make the batter.
In a blender, place the milk, eggs, flour blend, and salt, and blend just until smooth. You do not need a high-speed blender for this task. The batter will be thin.
Remove the hot pan with the melted butter from the oven, and pour off excess butter, leaving just a coating on the pan.
Working quickly, pour the batter into the hot pan and return to the oven. Bake for 12 minutes.
Rotate the pan 180° and continue to bake until the pancake is puffed and golden brown all over (about another 5 minutes). Remove from the oven.
The pancake should lift easily from the pan. If it seems stuck on any sides, loosen it with a knife and slide it from the pan onto a wire rack. This will ensure that the bottom of the pancake doesn’t become soggy as it cools.
Allow to cool briefly before slicing into 6 wedges and serving warm, garnished with fruit (in the winter, I like to serve it with citrus; in the summer, with berries), a light dusting of confectioners’ sugar, and maybe a dollop of whipped cream.
Any leftover wedges can be stored at room temperature for about 4 hours, or even wrapped tightly and stored in the refrigerator for at least 1 day.
Reheat gently in the microwave before serving. This recipe can be doubled easily, and baked in two batches.