Preheat the oven to 350°F (180°C). Spray a 9x5 inch loaf pan with non-stick spray and line it with parchment paper, letting the parchment paper hang over the sides so that the cake can be easily lifted out. Set aside.
Add vegan butter and white granulated sugar to the bowl of your stand mixer and cream them together until well mixed. Add vanilla extract and lemon extract and mix in.
Prepare vegan buttermilk by adding 1 tablespoon of lemon juice to a measuring jug and then adding soy milk up to the 1 cup (240ml) line. Let it curdle.
Add the vegan buttermilk to the mixer and mix it in with the vegan butter and sugar mix. It will look curdled but this is fine.
Sift the all purpose flour into a separate mixing bowl, add baking powder and salt and mix together.
Add the dry ingredients in with the wet and mix into a batter with a spoon. Be careful not to overmix.
Add lemon zest and mix in. The batter will be thick.
Transfer the batter to your prepared 9x5 loaf pan and smooth down.
Place into the oven to bake at 350°F for 60 minutes. At the 40 minute mark, bring it out and tent the top with foil* so that the foil makes a tent shape over the top. Return it to the oven to bake for the final 20 minutes.
Lift the cake out using the parchment paper overhang and place it onto a wire cooling rack to cool completely before adding the lemon glaze.
To make the glaze, mix powdered sugar, lemon juice and lemon extract in a bowl.
Spoon the glaze onto the cake and spread it around the top evenly. Allow the glaze to set in the fridge for 10 minutes before slicing and serving the cake.