Preheat the oven to 180°C /160°C fan (350°F). Grease and line two 20cm/8” cake tins.

In a medium bowl, whisk together the flour, cocoa powder, salt, bicarbonate of soda, and baking powder.

In a large mixing bowl using an electric hand or stand mixer, beat the butter, oil, and sugar together on medium speed until fluffy, about 3 minutes. Beat in the eggs, one at a time, until well combined, then beat in the vanilla.

In a liquid measuring cup, stir together the buttermilk, vinegar, and red food colouring. Use enough to make the liquid is bright red. (The more you add, the brighter the cake layers will be.)

While mixing on low speed, add a third of the flour mixture to the butter mixture, then add half of the buttermilk mixture. Repeat with another third of flour, then the remaining half of the buttermilk, ending with the rest of the flour. Stop and scrape down the bowl occasionally.

Divide the cake batter among the prepared tins and bake for 35 minutes or until the centers are springy to the touch. Let cool in the tins for 15 minutes then invert the cakes and cool completely on a wire rack. Remove the baking paper.

Beat the butter in a large mixing bowl on medium speed until very soft and spreadable. Add the cream cheese and beat until soft and fluffy, about 2 minutes. Beat in the vanilla.

While mixing on low, gradually mix in the icing sugar until well combined. Stop and scrape down the bowl occasionally during mixing. Increase the speed to medium dn beat until fluffy, about 1 minute.

Place on sponge on a cake stake and spread about a quarter of the frosting on top of the layer. Place the other sponge on top and spread the remaining frosting all over the top and sides of the cake.