For this recipe I decided to try out the Silly Yak Gluten Free Pastry. You could make your own pastry, or use a different brand of Gluten Free Ready Made Pastry if you like :)
A gluten free egg custard tart can easily be made dairy free too by either creating your own pastry without dairy... or by using a vegan & gluten free ready made pastry. I can recommend Voakes Free From who make Gluten Free & Vegan Pastry.
For the filling you will just need to use a high fat dairy free alternative to cows milk.