In a food processor, combine all-purpose flour and powdered sugar, pulsing until well blended. Add cold butter in chunks, mixing until the mixture resembles coarse crumbs. Then, incorporate the egg yolk and cold water, processing until the dough holds together, about 1-2 minutes. Wrap the dough in plastic wrap and chill in the refrigerator for 30 minutes.

Preheat your oven to 350°F (175°C). Roll out the chilled dough on a lightly floured surface, then carefully press it into mini tart pans. Prick the bottoms with a fork to prevent bubbling, then line with parchment paper and fill with pie weights. Bake for 10-12 minutes until golden brown, then remove from the oven and let them cool completely.

In a medium saucepan, whisk together lemon juice, zest, sugar, and eggs over medium heat until the mixture thickens, stirring constantly for about 8-10 minutes. Once thickened, remove from heat and whisk in butter until completely smooth. Pour this luscious lemon curd into the cooled tart shells, smoothing the tops with a spatula, and then refrigerate for at least 1 hour to set.

Prepare the lilac meringue by placing egg whites, granulated sugar, and cream of tartar in a heatproof bowl over simmering water. Whisk continuously until the mixture is warm and sugar is dissolved. Remove from heat and beat with an electric mixer for about 5-7 minutes until stiff peaks form. Gently fold in vanilla extract and violet food coloring to achieve a beautiful lilac hue.

Once the meringue is ready, pipe it onto the chilled mini lemon tarts in whimsical swirls. Use a kitchen torch to carefully toast the tips of the meringue until they reach a golden hue, creating a stunning visual appeal. Finally, garnish with edible lilac petals or dried lavender for a delightful touch that complements the flavor of your Mini Lemon Tart with Lilac Meringue.