Preheat oven to 250°F. Line a baking sheet with parchment paper.
Pulse the sugar in a blender or food processor for 30 seconds, until it resembles soft, fine sand (or use superfine sugar).
In a clean metal or ceramic bowl, whisk the egg whites and salt using a hand or stand mixer. Start at the lowest speed and gradually increase to medium. When the whites are foamy, add the cream of tartar. Beat until soft peaks form and slowly add the sugar, 1 tablespoon at a time. Beat until the sugar dissolves and the meringue develops stiff, shiny peaks. Sift the cornstarch over the bowl and fold in gently. Fold in the vanilla extract.
Using a large spoon, form the meringue into 6 rounds on the baking sheet, approximately 1. inches apart. Make a small divot in the top of each round to cradle the fruit.
Bake the meringues for approximately 45–60 minutes, or until they are dry on the outside and still pale. When they are done, turn off the heat and let the meringues cool completely in the oven before serving.
Meanwhile, make the creme anglaise. Prepare an ice bath by filling a large bowl with ice. Set a medium bowl on top of the ice.
Combine half and half and spices in a saucepan over medium heat. Bring to a simmer and remove from heat.
In another bowl, whisk egg yolks and sugar until pale and creamy, about 2 minutes. Slowly drizzle the warm cream into the egg and sugar mixture, whisking constantly. Return the mixture to the pan and cook over medium heat, stirring constantly, until the sauce thickens and coats the back of a spoon.
Pour the custard through a fine-mesh sieve into the bowl on top of the ice. Cover with plastic wrap and refrigerate until cool.
Just before serving, prepare apples. Melt butter in a large skillet over medium heat. Saute apples with sugar, spices and pecans until tender and golden, approximately 10 to 15 minutes. Alternately, prepare apples in advance and reheat before plating.
Spoon warm apples on pavlova and top with custard.
The elements can be made a day or two in advance. Store the apples and custard in the fridge and the pavlova in an airtight container at room temperature.