Preheat the oven to 175°C and grease and line either one large or several small, bottomless cake tins.
Place the butter, sugar & vanilla in the bowl of an electric mixer and beat on medium-high speed until creamy. Add the egg yolks, one at a time, and beat until combined. Sift the flour, baking soda and salt into a separate bowl, then add the coconut. With the mixer on a low speed add half of the dry ingredients, followed by half the milk. Repeat this step with the remaining ingredients. Be careful not to overmix or the cake will be tough.
Scrape the batter into prepared tins, and bake for 25minutes if you’re making one large cake or approximately 15 minutes for smaller cakes. You’ll know it’s ready when you can insert a knife and it comes out clean.
Meanwhile, prepare the plums. Cut each plum in half, discard the stone and cut each half into 4 segments. Once the cake had cooked, arrange the plums on top in one single layer.
Next make the meringue. Add the eggwhites to the bowl of your mixer and beat on medium-high speed. Once they start to foam, add the sugar one teaspoon at a time with the mixer running. Continue to whisk on high speed until the egg whites are thick and glossy. Next, add the cornflour, vanilla and vinegar, and whisk again until just combined. Use a spatula to scrape the meringue on top of the cakes, which should now be covered in slices of plum. You can make the meringue as smooth or as textured as you like. Reduce the oven temperature to 165°C and bake for 45-60 minutes depending on the size of your cake. Allow to cool before serving.