Using 6 eggs, carefully separate the yolks from the egg whites. Place egg whites in a small dish and allow it to sit until it reaches room temperature. Set yokes aside in a separate dish for the cranberry curd recipe.
Preheat the oven to 200 degrees F. Line two baking sheet pans with parchment paper and set aside.
In a stand mixer or with an electric hand mixer; whip the egg whites on HIGH for 1 minute, or until a soft peak forms. With the mixer still on, gradually add the superfine sugar a little bit at a time until it has fully dissolved. Continue beating at HIGH speed for 8 additional minutes or until a stiff peak forms.
Once a stiff peak forms, gently stir in the lemon juice, vanilla extract and corn starch (or cream of tartar if using). Transfer the meringue into a piping bag with a large tip (if you don’t have a piping bag, you can use a large spoon to scoop dollops in the next step).
Place a sheet of parchment paper on a baking sheet. Pipe or spoon the meringue into 3-inch round mounds, leaving slightly a hole in the middle (this will later be for filling).
Bake for 1 hour in a preheated oven. Next, turn the oven off and keep the door closed until fully cooled (about 1 hour). Do not assemble until 30 minutes before you want to serve. Prepare the cranberry curd while you wait.
When ready to serve, place a healthy scoop of cranberry curd in the middle of each pavlova. Next, top with whipped cream and garnish with sugared cranberries and fresh rosemary sprigs.