Top airy meringue with silky creme anglaise and sticky-sweet caramel to create this "floating island."
Preheat oven to 375 degrees. Brush a 10- to 12-cup Bundt pan with oil, and invert onto a paper towel to drain excess.
Make the meringue: Bring a kettle of water to a boil. Whisk egg whites, cream of tartar, and 1/4 teaspoon salt with a mixer on medium speed until soft peaks form. Whisk in superfine sugar, 1 tablespoon at a time, gradually increasing speed to high. Beat until stiff, glossy peaks form, 3 to 4 minutes. Reduce speed to low, and whisk in vanilla.
Transfer meringue to pan, pressing to remove air pockets. Smooth with a small offset spatula. Set Bundt pan in a roasting pan; transfer to oven. Carefully pour boiling water into roasting pan to reach 2 inches up sides of Bundt pan. Bake until meringue is puffed and lightly browned, about 20 minutes. Transfer Bundt pan to a wire rack. Let cool.
Make the creme anglaise: Combine milk and cream in a saucepan. Scrape vanilla seeds into pan, and add pod. Bring to a simmer over medium heat. Whisk together egg yolks, sugar, and a pinch of salt. Pour half the milk mixture into yolk mixture, whisking constantly. Return entire mixture to pan. Cook over medium heat, stirring constantly, until mixture is thick enough to coat the back of a spoon, about 5 minutes. Strain through a fine sieve into a bowl. Press plastic wrap directly onto surface to prevent a skin from forming. Refrigerate until cool, about 2 hours.
Unmold meringue onto a cake plate. Refrigerate until ready to serve. Make the caramel: Fill a medium bowl with cold water. Heat sugar and 3 tablespoons water in a small saucepan over high heat, swirling, until sugar dissolves. Raise heat to high. Bring to a boil. Cook, swirling occasionally, until dark amber, 3 to 6 minutes. Reduce heat to medium. Carefully stir in remaining 1/2 cup water (mixture will sputter), and swirl to combine. Cook until caramel reaches 230 degrees on a candy thermometer. Remove from heat. Dip bottom of pan into bowl of cold water to cease cooking. Drizzle caramel over meringue, then slice, and transfer to plates. Drizzle with creme anglaise.
Meringue can be refrigerated for up to 3 hours. Creme anglaise can be refrigerated for up to 2 days.