PAVLOVA
Preheat oven to 250°F. Draw a 9-inch circle on a piece of parchment paper. Flip the paper so ink does not get on the meringue and set aside.
Whip whites, salt, and vanilla seeds on high in a mixer until firm. With the motor running, add sugar, a spoonful at a time, until whites are glossy and very stiff.
Gently fold potato starch and vinegar into meringue with a spatula.
Transfer meringue to prepared parchment paper. Form meringue into a rustic bowl. It's not necessary to make it perfect. Just be sure to make the center thick enough to support the filling.
Bake pavlova at 250°F for 1½ hours. Turn off the oven and do not open the door for at least 6 hours or, better yet, overnight. The residual heat will crisp up the meringue and keep humidity out.
Place pavlova on a serving platter and dollop coconut mascarpone on meringue. Arrange pineapple on top and garnish with chopped macadamias and toasted coconut.
COCONUT MASCARPONE
With a mixer, or by hand, whip cream and sugar in a chilled bowl with chilled beater until soft folds forms.
Fold whipped cream into mascarpone cheese. Fold in coconut and vanilla bean seeds.
Keep chilled for up to 1 day before using.
ROASTED PINEAPPLE
Preheat oven to 400°F.
Place pineapple, sugar, butter, vanilla, and rum or orange juice in a baking dish. Roast pineapple, in a 400°F oven, for 30 minutes until browned and very fragrant. Occasionally spoon pan juices over fruit during cooking.
Remove form oven and cool pineapple before cutting into bite-size pieces. Use to top Brown Sugar Pavlova.