Preheat the oven to 180°C/350°F/gas mark 4. Grease an approx 11.5 x 21.5 cm / 4.5 x 8.5 in 2lb loaf tin and line with baking parchment.
Sift together the self-raising flour, bicarbonate of soda and salt. Set aside.
Place the silken tofu, non-dairy milk, lemon juice, sunflower oil, lemon zest and vanilla extract in a blender and blend until completely smooth. Set aside.
In a large bowl, whisk together the softened vegan block butter and caster sugar with an electric mixer until well combined.
Add half of the wet ingredients to the butter sugar mixture and whisk until smooth, the mixture will look a bit split but that’s ok.
Add half of the dry ingredients and whisk to combine then whisk in the rest of the wet followed by the rest of the dry. Once you have added all of the flour be careful not to over-beat the batter as that can make the cake tough. Just whisk it until it is smooth then stop.
Pour the batter into a greased and lined loaf tin and spread it level. Bake the cake for 50-60 minutes until golden and a skewer inserted into the centre comes out clean. The cake will be flat rather than domed on top.
Leave it to cool in the tin for ten minutes then carefully turn it out onto a wire rack and leave to cool completely.
To make the glaze simply stir enough lemon juice into the sifted icing sugar to create a thick but pourable consistency then drizzle it over the top of the cooled cake.