Pulse flour and powdered sugar in a food processor until combined. Add cold butter and blend until coarse crumbs form.

Incorporate egg yolk and water, blending until a dough forms. Wrap and chill for 30 minutes.

Preheat oven to 350°F (175°C). Roll out dough and press into mini tart pans. Bake for 10-12 minutes until golden.

Whisk together lemon juice, zest, sugar, and eggs in a saucepan. Cook while stirring until thickened (8-10 minutes).

Remove from heat and stir in butter until smooth. Let cool and refrigerate for 1 hour.

Combine egg whites, sugar, and cream of tartar over simmering water, whisking until warm and sugar dissolves.

Beat in stand mixer until stiff peaks form. Fold in vanilla and violet food coloring.

Pipe meringue atop each tart. Use a kitchen torch to lightly toast the meringue until golden.

Garnish with edible lilac petals or dried lavender.