Pulse together all-purpose flour and powdered sugar in a food processor until combined. Add cold butter until the mixture resembles coarse crumbs. Add egg yolk and just enough water to form a dough. Chill for 30 minutes while preheating the oven to 350°F (175°C). Roll out the dough, press into mini tart pans, prick the bases, and bake for 10-12 minutes until golden. Cool completely.

In a saucepan over medium heat, whisk together fresh lemon juice, lemon zest, granulated sugar, and whole eggs, stirring continuously for about 8-10 minutes until thickened. Remove from heat, whisk in unsalted butter until smooth, and let chill for about 1 hour.

Set up a double boiler, whisk together egg whites, granulated sugar, and cream of tartar until warm. Beat with an electric mixer for 5-7 minutes until stiff peaks form. Fold in vanilla extract and violet food coloring.

Once cooled and set, spoon lemon curd into tart shells. Use a piping bag to pipe lilac meringue onto the tarts, then lightly toast the tips using a kitchen torch.

Garnish each tart with edible lilac petals or dried lavender sprinkles. Arrange on a serving platter and serve chilled for a refreshing spring delight.