How to Make It
Make the rhubarb: Preheat oven to 325°F. Combine wine, 3/4 cup sugar, vanilla bean, and lemon peel strips in a medium saucepan. Bring to a simmer over medium, and cook until reduced to about 2/3 cup, about 15 minutes. Stir in lemon juice, vanilla extract, rosewater, and remaining 3 tablespoons sugar.
Trim and discard ends of rhubarb stalks, and rinse stalks. Cut stalks into 3/4-inch-thick slices on a deep diagonal. Transfer sliced rhubarb (about 6 1/2 cups) to a 13- x 9-inch baking dish. Pour syrup evenly over rhubarb.
Bake in preheated oven 10 minutes. Remove pan from oven, and gently tilt pan and spoon syrup over rhubarb to glaze it. Return to oven, and bake until rhubarb is soft but not mushy, about 20 minutes. Remove from oven, and glaze once more with syrup. Let stand until cool. Refrigerate rhubarb up to 1 week (it gets ﬁrmer and brighter as it sits).
Make the pavlovas: Preheat oven to 250º F. Combine egg whites, cream of tartar, and salt in a bowl. Beat with a mixer on medium-high speed until egg whites hold medium peaks (more than soft, but not yet firm), about 3 minutes. With mixer running, gradually add 1 cup sugar, 1/4 cup at a time, over the course of 3 minutes. Add cornstarch to remaining 1/4 cup sugar; stir until no lumps remain. Add sugar-cornstarch mixture to egg mixture; beat until mixture is firm and glossy, about 3 minutes. Add vinegar; beat until combined, about 30 seconds.
Line a baking sheet with parchment paper, and secure paper to pan by dabbing a bit of meringue underneath corners. Dollop meringue into six individual poofs, going for height over width (3 to 4 inches in diameter). Using the back of a spoon, make a deep divot in the center of each poof. Bake in preheated oven until firm, pale, opaque, and the surface cracks when pressed, about 45 minutes. (The interiors will remain slightly soft and marshmallowy.)
Finish the dish: Just before serving, beat cream and sugar to soft peaks with an electric mixer. Fill each pavlova with 2 to 3 tablespoons whipped cream, and top each with 1/2 cup rhubarb. Drizzle each with 2 1/2 tablespoons rosé syrup; garnish with pistachios.