Pre-heat oven to 170°C /160°C fan/gas mark 4.
Lightly grease the doughnut tin with non-stick cooking spray.
Pour the non-dairy milk and the lemon juice into a large jug and whisk together. Leave for five minutes for the milk to sour.
Whisk the caster sugar, coconut oil, eggs and vanilla extract into the jug and set aside for a moment.
Sift the oat flour, tapioca flour, potato flour, raspberry powder, baking powder, bicarbonate of soda and salt into a large mixing bowl, whisking to combine.
Make a well in the centre of the dry ingredients then pour the wet ingredients into it, using a wooden spoon to bring the batter together. Beat by hand until the batter is smooth and thickened.
Pour the batter carefully into each doughnut ring in the tin, filling to about three-quarters full.
Bake for 8 minutes.
Remove from the oven, leave for a couple of minutes for the doughnuts to settle then gently insert them out of the tin to cool on a cooling rack.
Wash the tin, re-grease and make the second batch, then the same again for the final 3 doughnuts.