In a food processor, combine flour and powdered sugar, pulsing until well mixed. Add cold butter, processing until the mixture resembles coarse crumbs. Incorporate the egg yolk and a splash of cold water, blending until a dough forms. Chill the dough for 30 minutes, then roll it out and press into mini tart pans. Prick the bottoms with a fork, line with parchment, and bake at 350°F for 10-12 minutes until golden brown. Allow to cool completely.

In a medium saucepan, whisk together the lemon juice, zest, granulated sugar, and eggs over medium heat. Cook the mixture, stirring constantly for 8-10 minutes, until it thickens and coats the back of a spoon. Remove from heat and whisk in butter until the mixture is smooth and glossy. Carefully fill the cooled tart shells with lemon curd, and refrigerate for at least one hour to set the curd.

Set up a heatproof bowl over simmering water to create a double boiler. Combine egg whites, sugar, and cream of tartar in the bowl, whisking continuously until warm, about 3-5 minutes. Remove from heat and beat the mixture on high speed until stiff peaks form, adding in the vanilla extract and violet food coloring until the desired hue is achieved. Use a piping bag to swirl the lilac meringue atop each tart.

Using a kitchen torch, carefully toast the tips of the meringue until lightly golden. For an extra touch of elegance, garnish each tart with edible flowers. Serve immediately for the best presentation and flavor experience.