Preheat oven to 180°C / 160°C Fan / 350°F / Gas Mark 4. Grease and line a 900g / 2lb loaf tin with parchment paper and set aside.
In a food processor, process the shelled pistachios until they're a crumb like consistency. Set this mixture aside for later on.
Place a sieve over a large mixing bowl and sift the flour, baking powder, bicarbonate of soda and sugar. Give these ingredients a quick stir together to combine. Add the pistachio crumbs and lemon zest (zest of one lemon) to the bowl and mix.
In a small jug, whisk together the juice of the lemon you zested earlier, along with the melted baking block/dairy-free spread or vegetable oil and the plant milk. Add these wet ingredients to the dry and gently fold together until no lumps of flour remain - be careful not to over mix the cake batter.
Pour the cake batter into the loaf tin and bake for 45-60 minutes or until a cake tester comes out clean without any uncooked batter remaining. Test directly in the centre of the cake to ensure it's baked all the way through. Mine took about 55 minutes to bake fully, but all ovens are different so keep checking.
Once the cake has baked, prepare the lemon syrup. In a small bowl or jug, stir the lemon juice with the sugar until all the sugar has dissolved. Take a tooth pick and prick holes all over the top of the cake. Pour the syrup over the warm cake and leave it cool in the tin for at least 30 minutes, then carefully remove from the tin and place on a wire rack to finish cooling completely.
Now the cake is cool, prepare the lemon glacé icing. In a small bowl, stir together the icing sugar with enough lemon juice until you have a thick but slightly runny icing.
Drizzle the icing over the cake as you desire and decorate with an sprinkle of extra chopped pistachios. Allow the icing to set before slicing. Store the cake in an airtight container or a cake plate with a cover for up to 3 days.