- Mix together flour, xanthan gum, salt, sugars in food processor or mixer. 
- Add butter pieces and mix until incorporated. I usually pulse or mix about 10 seconds. 
- Mix egg wth vanilla. 
- Stream in egg mixture. 
- Add cold water 1 teaspoon at a time until dough forms. 
- Turn dough onto sheets of plastic. 
- Flatten, wrap well in plastic and refrigerate for one hour. 
- Once you are ready to roll, take out and, if necessary, let it sit out on counter to soften a little. 
- Roll into a 12 inch round. Don't worry if it's not perfectly round. 
- Put dough in tart pan and reserve scraps to press in. 
- Place prepared tart pan in freezer for for about 15 minutes, prior to baking. 
- Bake and fill as needed for recipes. 
- If you need to bake completely without filling (for a fruit tart for example), bake for 25 minutes at 375 degrees F. 
- Cover with Parchment paper that has been greased or sprayed with a baking spray. 
- Fill with pie weights (or dried beans). Make sure to cover edges so they don't burn. 
- Cool completely before filling.