Prepare the Tart Shell Dough: In a food processor, pulse together 1 ¼ cups of all-purpose flour and ¼ cup of powdered sugar until combined. Add ½ cup of cold cubed unsalted butter, pulsing until the mixture resembles coarse crumbs. Incorporate 1 large egg yolk and 1–2 tablespoons of cold water, pulsing until the dough forms. Wrap it in plastic wrap and chill in the fridge for 30 minutes.

Bake the Tart Shells: Preheat your oven to 350°F (175°C). On a lightly floured surface, roll out the chilled dough to about ¼ inch thick. Press the dough into mini tart pans, ensuring an even layer. Prick the bottoms with a fork to prevent bubbling, then line with parchment paper and fill with pie weights. Bake for 10–12 minutes until golden and firm, then cool completely on a wire rack.

Make the Lemon Curd: In a medium saucepan, whisk together ½ cup of fresh lemon juice, 1 tablespoon of lemon zest, ¾ cup of granulated sugar, and 3 large eggs. Cook over medium heat, stirring constantly for about 8–10 minutes, or until the mixture thickens and coats the back of a spoon. Remove from heat and stir in 6 tablespoons of cubed unsalted butter until smooth. Let it cool slightly before filling the tart shells.

Chill the Lemon Tarts: Once the lemon curd is prepared, carefully fill each mini tart shell with the warm lemon curd mixture. Spread the curd evenly using a spatula and refrigerate the tarts for at least 1 hour until set.

Prepare the Lilac Meringue: In a heatproof bowl, combine 3 large egg whites, ¾ cup of granulated sugar, and ¼ teaspoon of cream of tartar. Place the bowl over simmering water, whisking continuously until warmed and the sugar is dissolved. Remove from heat and beat with an electric mixer for 5–7 minutes until stiff peaks form. Gently fold in ½ teaspoon of vanilla extract and a few drops of violet food coloring.

Assemble the Tarts: Using a star tip, pipe the lilac meringue generously on top of the chilled lemon tarts. Create swirls and peaks for presentation and lightly toast the tips of the meringue with a kitchen torch.

Garnish and Serve: Garnish each tart with optional edible lilac flowers or dried lavender just before serving.