Preheat your oven to 180°C/350°F (or 160°C/325°F if you're using a fan or convection oven).

Grease, flour and line two 7-inch cake tins.

Mix the soy milk and vinegar together and set aside.

In a large bowl, mix the flour, baking soda, sugar and matcha powder together.

Add the soy milk mixture along with the melted margarine and vanilla extract. Mix well until you have a smooth cake batter. Make sure to get any dry bits from the bottom of the bowl.

Divide the cake mix equally between your two cake tins. Bake for 18-20 minutes, until a toothpick through the centre comes out clean.

Let the cakes cool in the tins for 5 minutes then flip them out on a wire rack to cool completely.

In a large bowl, soften the margarine using a wooden spoon then stir in the vanilla extract.

Mix in the icing sugar, a little bit at a time.

Using an electric whisk or stand mixer, whisk the frosting for a minute or two until it becomes smooth, pale and fluffy. It should be a spreadable consistency but if you need to loosen it a bit, just add a splash of plant-based milk. If it's too runny, you can add more icing sugar.

Place the first cake layer on a plate or cake stand. Spread a thick layer of buttercream onto it.

Add the second cake layer on top and repeat. You can leave it like this or you can coat the sides of the cake in buttercream too.

Let the cake sit at room temperature for around an hour, to let the icing harden, then cut into slices and enjoy!