In a food processor, blend together all-purpose flour and powdered sugar until combined. Add the cold butter, pulsing until the mixture resembles coarse crumbs. Mix in the egg yolk and gradually add ice water until a dough forms. Chill the dough for 30 minutes.

Preheat your oven to 350°F (175°C). Roll out the dough and press it into mini tart pans, pricking the bases with a fork. Line with parchment and baking weights, then bake for 10–12 minutes until golden. Let the shells cool completely.

In a medium saucepan, whisk together freshly squeezed lemon juice, lemon zest, granulated sugar, and eggs. Cook this mixture over medium heat, stirring continuously for 8–10 minutes until it thickens. Remove from heat and stir in butter until smooth. Pour the lemon curd into cooled tart shells and chill for at least 1 hour.

In a heatproof bowl, whisk together egg whites, granulated sugar, and cream of tartar until warm. Beat the mixture on high speed for about 5–7 minutes until stiff peaks form. Gently mix in vanilla extract and optional violet food coloring. Pipe the lilac meringue onto the cooled tarts.

Using a kitchen torch, toast the peaks of the lilac meringue until lightly golden. Garnish with edible lilac petals or dried lavender before serving.