Start by preheating the oven to 180C and lining a loaf tin with baking/parchment paper.
Grab a medium bowl or jug and pour in the soya milk and apple cider vinegar and stir, set aside (this will quickly curdle to create a vegan 'buttermilk')
In a large bowl, sieve the dry ingreients: plain flour, baking powder, bicarbonate of soda, salt and spices and stir.
Add the remaining wet ingredients to the milk and vinegar mixture and whick until well combined.
Pour the wet mixture into the dry and fold until the cake batter forms.
Pour into the lined tin, spread until even and place in the centre of the oven to bake for 45 minutes, or until a skewer comes out clean. It should be cooked through but still moist.
Make the cinnamon buttercream: add all the ingredients to a large bowl and mix using a hand mixer and spread over the loaf - make sure it has cooled completely before adding the buttercream. Enjoy! Store in an airtight container.