Heat the milk, butter, ½ cup sugar, and salt in a saucepan over medium-high heat until the butter begins to melt. Remove from the heat and stir, then let sit until the butter has completely melted and the mixture is cooled to lukewarm.
In a large bowl, combine the warm water, the remaining 1 tbsp sugar, and yeast and let stand until the mixture is foamy and the yeast is activated, about 5 minutes.
Whisk the eggs into the yeast mixture. Then whisk in the cooled milk mixture.
In a separate bowl, whisk together the flour and xanthan gum. Then add the flour mixture to the egg mixture and stir vigorously until the dough is smooth. It will be sticky.
Roll out the dough between two large sheets of plastic wrap to form a rectangle that is about 18 inches wide by 12 inches.