1-First Step: Prepare your oven and pan Preheat the oven to 180ºC fan (350°F). Line an 8×8 inch or 7-inch square cake tin with greaseproof paper, allowing it to hang over the edges for easy removal after baking.

2-Second Step: Make the vegan buttermilk Mix the dairy-free milk with apple cider vinegar and set aside for 5-10 minutes to curdle, creating a vegan buttermilk substitute that helps activate leavening and produce a lighter crumb.

3-Third Step: Combine dry ingredients Sift together the flour, caster sugar, baking powder, and bicarbonate of soda in a large bowl. Mix well to blend ingredients evenly for consistent rise and texture.

4-Fourth Step: Mix wet ingredients Whisk the sunflower oil and vanilla extract into the curdled milk mixture, combining fully to ensure moisture is evenly distributed throughout the batter.

5-Fifth Step: Combine wet and dry mixtures Pour the wet mixture into the dry ingredients, mixing gently until just combined. Be careful to avoid over-mixing to keep the cake tender and light.

6-Sixth Step: Divide and flavor the batter Divide the batter equally into three bowls. Leave one plain for the vanilla layer, add cocoa powder to the second for the chocolate layer, and mix the strawberry flavoring or freeze-dried strawberry powder with a drop of pink food gel into the third bowl for the strawberry layer.

7-Seventh Step: Layer and swirl the batters Spoon the batters alternately into the prepared tin, one color at a time. Use a skewer to gently swirl the layers, creating a marbled effect while preserving distinct colors.

8-Eighth Step: Bake and cool Bake the cake for 25-30 minutes, or until a skewer inserted comes out clean. Let it cool in the tin for 10 minutes, then transfer to a wire rack to cool completely before frosting.

9-Final Step: Prepare and apply the buttercream Whip the dairy-free butter until creamy. Gradually beat in the sifted icing sugar, adding dairy-free milk to achieve the desired consistency. Divide the buttercream into three bowls: plain, chocolate (add melted dark chocolate), and strawberry (add pink food gel and strawberry flavoring or powder). Pipe lines of each color over the cooled cake and gently spread to blend while keeping swirls visible. Optionally decorate with white sprinkles.