Making the Lemon Pavlovas:

1. Preheat Oven: Set to 250°F. Line two baking sheets with parchment paper.
2. Whip Egg Whites: In a mixer, whip egg whites on medium speed for 1 minute. Gradually add the sugar, a little at a time.
3. 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.
4. Add Flavors: Gently fold in cornstarch, lemon juice, and lemon zest.
5. 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.
6. 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.

Making the Lemon Curd:

1. Cream Butter: In a mixer, beat butter on medium speed for 1 minute.
2. Add Sugar and Eggs: Add sugar and beat for 2 minutes. Mix in eggs one at a time until fully combined.
3. Add Lemon: Stir in lemon juice and zest. The mixture might look separated, but it will come together when cooked.
4. Cook Curd: Transfer to a saucepan and cook on medium-low, stirring constantly, for 10-15 minutes until it thickens and reaches 170°F or coats the back of a spoon heavily.
5. Cool and Chill: Pour curd into a bowl, cool, and refrigerate for at least 2 hours.

Assembling the Pavlovas:

1. Fill Pavlovas: Spoon lemon curd into the center of each pavlova.
2. Top with Berries and Coconut: Add mixed berries and toasted coconut flakes. Dust with powdered sugar before serving if desired.