Make the Tart Shells
In a food processor, pulse flour and powdered sugar. Add the cold butter and pulse until crumbly. Add egg yolk and water; pulse until the dough just comes together. Wrap and chill for 30 minutes. Preheat oven to 350°F (175°C). Roll out dough and press into mini tart pans. Prick the base with a fork, line with parchment and pie weights. Bake for 10–12 minutes until golden. Let cool completely.

Prepare the Lemon Curd
In a saucepan, whisk together lemon juice, zest, sugar, and eggs. Cook over medium heat, stirring constantly until thickened (about 8–10 minutes). Remove from heat and whisk in butter until smooth. Let it cool slightly, then pour into tart shells. Chill for 1 hour to set.

Make the Lilac Meringue
In a heatproof bowl over a saucepan of simmering water, whisk egg whites, sugar, and cream of tartar until warm and sugar dissolves. Remove from heat and beat with an electric mixer until stiff peaks form (about 5–7 minutes). Add vanilla and a drop of violet food coloring to achieve a soft lilac hue. Pipe onto chilled lemon tarts using a star tip.

Toast and Garnish
Use a kitchen torch to lightly toast the meringue tips. Garnish with edible lilac petals or dried lavender for a stunning finish.