Preheat your oven to 250°F (120°C) and line a baking sheet with parchment paper. In a mixing bowl, whisk egg whites until soft peaks form. Gradually add sugar, whisking until glossy and stiff peaks form, about 5–7 minutes. Fold in cornstarch and vinegar until combined.

Spoon the meringue onto the prepared parchment, shaping it into a circular disk with a slight indent in the center. Bake for 1 hour until crispy. Turn off oven and cool inside for at least 3 hours.

Melt butter in a skillet over medium heat. Add sliced apples, brown sugar, lemon juice, cinnamon, and vanilla. Cook for 10 minutes until apples are tender. Remove from heat and let cool.

In a mixing bowl, pour heavy whipping cream and add sugar and cinnamon. Beat on medium speed until foamy, then increase to medium-high until stiff peaks form, about 2–4 minutes.

Transfer cooled pavlova to a serving dish and spread cinnamon whipped cream on top. Layer with caramelized apples and drizzle with syrup. Serve immediately.