Preheat your oven to 225°F (110°C) and line a baking sheet with parchment paper.

In a clean, dry mixing bowl, beat egg whites with an electric mixer on medium speed until foamy.

Gradually add granulated sugar, one tablespoon at a time, until glossy, stiff peaks form, about 8-10 minutes.

Gently fold in cornstarch and vinegar until well combined.

Spoon or pipe the meringue mixture onto the baking sheet, creating nests approximately 3 inches wide with an indentation in the center.

Bake for 1.5 hours until dry and crisp, then turn off the oven and let cool completely inside.

Prepare the lemon curd by whisking lemon juice, sugar, and egg yolks in a saucepan over low heat, stirring frequently until thickened, about 10-15 minutes.

Remove from heat, stir in butter until smooth, and allow to cool slightly.

Once meringue nests are cool, spoon or pipe lemon curd into the centers and top with fresh berries.

Serve immediately or refrigerate briefly, garnishing with additional berries or powdered sugar if desired.