Preheat the oven to 350°F/ 180°C. Prepare 3 x 6 inch cake pans (or 3 x 8 inch cake pans) with parchment paper.
In your mixer bowl, cream butter and the first portion of sugar (230g /8.1oz) until light and fluffy for about 5 minutes.
Add the separated yolks, one at a time, while mixing.
Add the raspberry preserves and vanilla (and pink colouring if using) and mix through the batter.
Sift the AP flour, baking powder, salt together and set aside.
Add the flour in 3 batches, alternating with the milk (flour-milk-flour-milk-flour) while mixing on low.
In a clean, dry bowl whisk the egg whites until they are frothy. Add the sugar and cream of tartar and whisk until it forms stiff peaks and is glossy.
Add one quarter of the meringue into the cake batter and mix well.
Gently fold in the rest of the egg whites.
Evenly distribute the batter between the 3 cake pans and bake in the pre-heated oven for 20-30 minutes, or until a toothpick or cake tester inserted into the cake comes out clean. Remove from the oven, and let it cool for about 10 minutes and turn out on to a wire rack and let it cool completely.
When cooled, you can trim the top of the cake and frost the cake. You can store the cakes in the fridge for a few days, double wrapped in plastic wrap and foil, or for months in the freezer.