Preheat oven to 400 degrees. Grease a 9-inch cast-iron skillet with the softened butter. Set aside. Combine milk, sugar, Grand Marnier/brandy, vanilla, eggs and a pinch of salt. Whisk well in a bowl, or blend for a few seconds in a food processor or blender. Add the flour and mix until smooth.
Pour batter into prepared cast iron skillet. Distribute 1 ½ cups of cherries evenly over the batter. Bake for 18 minutes. Carefully place the remaining cherries on top of the batter. By doing this, you will have some of the cherries exposed for presentation instead of sinking into
the batter. Bake an additional 12 to 15 minutes or until a toothpick inserted into the center of batter comes out clean and crust is golden brown. Remove from oven and let cool for 20 minutes. Dust with powdered sugar if desired and cut into wedges.