Add the ricotta, eggs, caster sugar and vanilla extract to a large bowl and whisk together until smooth.
In a separate bowl mix together the plain gluten free flour, tapioca flour, baking powder and xanthan gum, plus a pinch of salt.
Pour the dry ingredients into the wet ingredients and mix together until it forms a very thick batter. Leave to rest for 10 minutes while you heat the oil.
Add the oil to a pan, around 2 inches deep. Heat to 165-175C (330-350F)
Once the oil is hot, use an ice-cream scoop to drop scoops of batter into the pan (tip - oil the scoop to make it easier as the batter can be quite sticky!). I usually do 3-4 scoops at-a-time, don’t overcrowd the pan.
Cook for 3 minutes, turning occasionally and making sure they don’t stick together. They should be a deep, golden brown all over. (Too pale = oil too cold, too dark = oil too hot).
Remove from the pan using a slotted spoon and onto a plate or bowl lined with kitchen towel. Repeat in batches until all the doughnuts are cooked.
Sprinkle liberally with icing sugar and serve straight away.
Video
Notes
If you don't have an ice-cream scoop you can use two spoons to drop bits of the batter into the oil. These will result in a more 'rustic' looking zeppole, rather than round balls.