Chocolate rainbow cake | Women's Weekly Food

Ingredients

• 4 cup flour
• 2 teaspoon baking powder
• 4 teaspoon baking soda
• 1 cup cocoa
• 1 teaspoon salt
• 3 cup sugar
• 4 eggs
• 2 cup milk, plus 2 tablespoons cider vinegar
• 2 teaspoon vanilla essence
• 1 cup canola oil
• 1 cup hot water
• Buttercream
• 500 gram butter, softened
• 12 cup icing sugar, sifted
• 1/2 cup milk
• gel food colours
• 6 piping bags and petal-tip nozzle