Meringue Swirls

Preheat oven to 200 degrees. Combine egg whites and sugar in a heatproof bowl. Add vanilla bean seeds. Set bowl over a pot of simmering water, and stir until sugar dissolves and mixture is warm, about 3 minutes. Add salt and cream of tartar.

Beat with a mixer on medium-high speed until stiff, glossy peaks form and meringue is mostly cooled, about 7 minutes. Beat in zest.

Using a small paintbrush, paint 3 vertical stripes of food coloring inside a pastry bag fitted with a 1/2-inch round tip (Ateco #805). Fill bag with meringue, and pipe 1 3/4-inch circular shapes (they don't need to be perfect rounds) 2 inches apart on 2 parchment-lined baking sheets. As you finish piping each shape, apply less pressure to pastry bag, and swirl the tip off in a circular motion.

Bake meringues until crisp on the outside but still soft inside, about 1 hour 15 minutes. Let cool completely on a wire rack.