In a food processor, pulse together the all-purpose flour and powdered sugar. Add the cold butter and pulse until the mixture resembles coarse crumbs. Mix the egg yolk with a splash of cold water, then combine it into the dough. Chill for 30 minutes, then preheat your oven to 350°F (175°C). Roll out the dough, press it into mini tart pans, prick the bases, line with parchment and weights, then bake for 10-12 minutes until golden brown. Let them cool completely.

In a saucepan, whisk together the fresh lemon juice, lemon zest, granulated sugar, and eggs until combined. Cook over medium heat, stirring constantly until the mixture thickens, about 8-10 minutes. Remove from heat and whisk in the unsalted butter until smooth. Allow to cool slightly before pouring into the cooled tart shells. Chill for 1 hour.

In a heatproof bowl over simmering water, whisk the egg whites, granulated 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. Gently fold in vanilla extract and violet food coloring.

Using a kitchen torch, toast the tips of the lilac meringue until light golden brown. Garnish with edible lilac petals or a sprinkle of dried lavender.