Preheat the oven to 175C. Line a 2lb loaf tin with parchment paper.
Remove the top and bottom of the courgette. Grate it on the coarse side of your grater.
Place the grated courgette in a sieve and sprinkle with 1/2 tsp of the salt. Mix it a little with your fingers or a fork to combine. Leave it suspended over the sink or a bowl while you get the rest of the ingredients. The salt will draw out the moisture from the courgette.
Meanwhile add the vinegar to the milk. Leave it for 10 to 20 minutes. The vinegar will curdle the milk, creating vegan buttermilk.
Finely chop the basil, spring onion and sun dried tomatoes. Do the basil and spring onion first because the tomatoes will make the board oily which is not ideal for chopping other things.
Add these to the measuring jug with the milk.
In a large mixing bowl combine the flour, nutritional yeast, baking soda and the other 1/2 teaspoon of salt. Stir well to combine.
Go back to the courgette and squeeze out all the liquid you can with your hands. You can do this by pushing the courgette against the side of the sieve. It should weigh about 185g after squeezing.
When it's as squeezed as you can get it transfer it to the measuring jug with the milk. Mix to combine.
Now add the courgette jug mixture to the flour mixture. Stir to combine, no need to over mix. Once it's combined it's done.
Transfer to the loaf tin. Use the pointy side of the spatula or a knife to score a line all the way along the top about 2cm deep. This will help the loaf to rise evenly.
Put it in the oven on a middle shelf. Make sure the shelf above it isn' too close as it will rise quite a bit when it's cooking.
Put on your timer for 30 mins after which time turn the loaf 180 degrees and put on the timer for another 30 mins. When the timer goes off a second time take a small sharp (not serated) knife or a metal skewer and insert it into the middle of the loaf. If it comes out clean the loaf is done. If there is any sticky mixture on the knife/skewer put it back in for 10 mins and check again. The loaf is done when the skewer comes out clean.
Leave it to cool for 10 mins in the tin before transferring to a cooling rack.
Leave to cool for at least an hour before slicing (if you can manage. Usually I cut off a crusty piece from the end after 10 minutes but you won't be able to get proper slices for at leas an hour).