With the rack in the middle position, preheat the oven to 180°C (350°F). Butter and flour 2 20-cm (8-inch) springform pans and line the bottoms with parchment paper.
In a bowl, combine the flour, baking powder, baking soda and salt. Set aside.
In another bowl, mix the vinegar, cocoa powder, food colouring and vanilla. Set aside.
In another bowl and using an electric mixer on medium speed, cream the butter, sugar and colouring mixture until light and fluffy. Add the eggs one at a time, beating until smooth. With the mixer on low speed, add the dry ingredients, alternating with the buttermilk. Divide the batter between the pans. Bake until a toothpick inserted in the centre comes out clean, about 40 minutes. Let cool slightly, then remove from the pans. Let cool to room temperature.
Italian Meringue Frosting
In a saucepan, bring the water, sugar and corn syrup to a boil and cook until it reaches 113°C (235°F) on a candy thermometer.
Meanwhile, in a large bowl and using an electric mixer on medium speed, beat the egg whites until soft peaks form. As soon as the sugar syrup reaches 113°C (235°F), slowly add it to the egg whites while beating (avoid pouring the syrup directly on the beaters). Continue beating until the meringue has cooled completely and forms stiff peaks, about 30 minutes.
Cut the cakes in half horizontally, making 4 layers. Spread half of the frosting between the 4 layers. Ice the top and sides with the other half of the frosting.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.