1. Preheat oven to 275 degrees. Line two baking pans with parchment paper. Set aside. In the bowl of a heavy-duty electric mixer fitted with the whisk attachment, beat egg whites, salt, vanilla extract, and cream of tartar on medium-high speed until medium peaks form. Slowly add sugar; continue beating until firm peaks form. Fold in cornstarch.

2. Transfer mixture to a large pastry bag. Use scissors to cut 3 inches off of the tip. Pipe mixture into eight large mounds onto prepared baking pans. Bake until meringues are crisp on the outside but their consistency resembles marshmallow on the inside, about 1 hour. Serve with poached rhubarb with strawberries, yogurt cream, and strawberry sauce.