Pavlova: Line rimless baking sheet with parchment paper. Using 10-inch (3 L) springform pan as guide, trace circle onto parchment paper. Turn parchment paper over. Set aside.
In food processor, pulse sugar until finely ground, about 30 seconds. In large bowl, beat egg whites with cream of tartar until soft peaks form; beat in sugar, 2 tbsp at a time, until stiff glossy peaks form. Beat in cornstarch, vinegar and vanilla.
Using 2 large spoons, drop egg white mixture by spoonful along inside of traced circle on prepared pan. Bake in 275°F oven just until no longer shiny, about 1 hour. Turn off heat; open door slightly and let cool completely in oven, about 2 hours.
Topping: While Pavlova is cooling, in small saucepan, bring cranberries, sugar, cinnamon stick, orange zest and 1/2 cup water to boil over medium-high heat. Reduce heat to low and simmer, stirring occasionally, until mixture is thickened and reaches jam-like consistency, about 10 minutes. Stir in blueberries. Let cool completely, about 1 hour. (Make-ahead: Cover and refrigerate for up to 5 days; stir in about 1 tbsp warm water to reach desired consistency.)
Spoon cranberry mixture over top of Pavlova. Garnish with bay leaves (if using). Serve immediately.
Makes 10 to 12 servings.