Grease a 1.5 to 2 litre pudding basin or Pyrex bowl. Pour in half of the golden syrup and the Tablespoon of lemon juice and stir to combine.
100 g (4 Tablespoons) golden syrup, 1 Tablespoon lemon juice
In a separate bowl, use a balloon whisk to whisk together the melted butter, sugar, milk, lemon juice and zest and vanilla extract.
75 g (⅓ cup) vegan butter, 100 g (½ cup) caster or granulated sugar, 120 g (½ cup) unsweetened non-dairy milk (I use soy), finely grated zest of 1 large lemon, 1 Tablespoon lemon juice, 1 teaspoon vanilla extract
Whisk in the baking powder followed by the flour. Mix until no dry lumps remain but be careful not to over-beat the batter.
¼ teaspoon baking powder, 160 g (1 + ⅓ cups) self-raising flour
Pour the batter into the pudding basin on top of the golden syrup.
Microwave uncovered on high for 5 minutes. The pudding should look dry on top and a skewer should come out clean or with a few crumbs but no wet batter. If it doesn't look quite done yet, microwave it for another minute.
Allow the pudding to rest for 10 minutes then loosen around the edge with a silicone spatula, going all the way down to the bottom of the bowl.
Carefully flip the pudding out onto a plate and drizzle with the rest of the golden syrup. Serve right away with custard or ice cream.