Preheat Oven: Set to 250°F. Line two baking sheets with parchment paper.
Whip Egg Whites: In a mixer, whip egg whites on medium speed for 1 minute. Gradually add the sugar, a little at a time.
Whip Until Stiff: Once all the sugar is added, increase speed to high and whip for 9 minutes, until stiff peaks form. Around minute 8, add food coloring if desired. The meringue should be glossy and firm.
Add Flavors: Gently fold in cornstarch, lemon juice, and lemon zest.
Pipe Meringue: Transfer meringue to piping bags fitted with an open star tip. Pipe into 3 1/2-inch nests on the baking sheets, leaving a slight indentation in the center for the filling.
Bake and Cool: Bake for 1 hour. Turn off the oven and leave the pavlovas inside for 30 minutes. Let cool completely before filling. Store unfilled pavlovas in an airtight container at room temperature for up to 5 days.