For the Roasted Rhubarb: Preheat oven to 400°. Cover a baking sheet with parchment paper. Place all ingredients in a medium-sized mixing bowl and mix with a spoon. Spoon the rhubarb mixture onto the baking sheet. Put in the oven for 20 to 25 minutes, until the rhubarb is tender. Stir several times during baking.
Remove from the oven and cool. Remove the cardamom pods before serving.
Whipped Cream: Place a small mixing bowl in the freezer until chilled. Place the cream, sugar and vanilla in the bowl. Mix on low speed until it begins to thicken and then increase the speed to medium. Beat until the cream forms soft peaks. Refrigerate until time to serve.
Meringue: Preheat oven to 350°. Place a piece of parchment paper on a baking sheet.
In a mixing bowl, whisk the egg whites until they form satiny, soft peaks. Add the sugar 1 tablespoon at a time until the mixture is stiff and shiny. Stop the mixer and sprinkle the cornstarch, lemon juice and vanilla over the egg white mixture. Turn the mixer back on low and mix for a few more seconds until combined.
Pour the egg white mixture onto the parchment paper in an 8- to 10-inch round circle. Smooth out to create an even thickness throughout the meringue.
Place pan in oven and immediately turn oven down to 300°. Bake for 1 to 1¼ hours. If the meringue begins to brown, turn oven down to 275°. When meringue no longer looks glossy and is crispy on the outside, shut off oven and open the door slightly. Allow meringue to cool for 1 to 2 hours this way. Remove from oven and turn onto a serving platter. Top with the roasted rhubarb and the whipped cream. Cut into slices and serve.
HINTS FOR MAKING A GREAT PAVLOVA
• Use egg whites that are room temperature.
• Make sure no yolk gets mixed into the whites.
• Ensure that your bowl and mixing tool are completely clean. Any oil or water will keep the eggs from whisking properly.
• Start the mixer on low speed until the whites begin to bubble and look frothy. Increase the mixer speed to medium.
• Be patient. Whisking egg whites takes time. Expect 5 to 8 minutes (potentially more).
• Soft peak means to beat egg whites or cream until it is fluffy enough that when the whisk is removed the peaks that are formed lift and then fall.