Preheat oven to 150°C. Line 3 large baking trays with baking paper and set aside.
Place sugars into mixing bowl and mill 10 sec/speed 9. Transfer into a separate bowl and set aside. Thoroughly clean and dry mixing bowl.
Insert butterfly whisk. Place egg whites and cream of tartar into mixing bowl and whip 4-6 min/37°C/speed 3.5, without measuring cup, until very stiff peaks form.
Mix 4 min/37°C/speed 3, slowly adding reserved sugar (1 teaspoon at a time), vinegar and vanilla through hole in mixing bowl lid. Mixture should be glossy and smooth. Remove butterfly whisk.
Divide meringue mixture evenly between 3 bowls. Add 2 tablespoons of the reserved cherry syrup to 1 bowl and gently combine using a metal spoon, taking care not to remove air from mixture. Add cocoa powder to another bowl, and gently swirl through to create a marbled effect. Do not add anything to last bowl of egg whites.
Using a piping bag with a round nozzle (1 cm), pipe each mixture into approx. 30 small circles (approx. 4 cm diameter) onto the prepared trays. Using a fine-mesh sieve, dust cherry meringues with freeze-dried cherry powder (optional) and dust chocolate meringues with extra cocoa powder.
Place trays into oven, reduce temperature to 110°C and bake for 1 hour (110°C). Turn off oven and leave meringues to cool completely with oven door shut (approx. 2 hours). Clean
and dry mixing bowl and butterfly whisk.