Preheat the oven to 350°F (175°C). In a food processor, combine all-purpose flour and powdered sugar, pulsing until well mixed. Add cold butter and pulse until the mixture resembles coarse crumbs. Incorporate the egg yolk and water until a dough forms. Chill for about 30 minutes, then press into mini tart pans. Prick the bottoms, line with parchment paper, and bake for 10–12 minutes until golden. Allow to cool completely.

In a medium saucepan, whisk together lemon juice, lemon zest, granulated sugar, and eggs over medium heat. Cook while stirring constantly for about 8–10 minutes until thickened and it coats the back of a spoon. Remove from heat and stir in butter until melted and smooth. Pour into cooled tart shells and refrigerate for at least 1 hour to set.

Prepare a heatproof bowl over simmering water. Add egg whites, granulated sugar, and cream of tartar, whisking gently until warm and sugar dissolves, about 5 minutes. Remove from heat and beat the mixture until stiff peaks form, about 5–7 minutes. Fold in vanilla extract and violet food coloring.

Pipe the meringue on top of the lemon curd in each tart shell, creating decorative swirls. Use a kitchen torch to lightly toast the tips of the meringue until golden. Garnish with edible lilac petals or a sprinkle of dried lavender.