In a food processor, pulse the flour and powdered sugar just to combine. Add the cold cubed butter and pulse until the mixture looks sandy with some pea-size bits.

Add the egg yolk and 1 tablespoon cold water, then pulse until the dough starts to clump. If it still looks dry and won’t clump, add the remaining 1 tablespoon water and pulse a few times.

Turn the dough out, press into a disk, and chill for 30 minutes.

Preheat the oven to 350°F. Roll the chilled dough out and press it into mini tart pans. Prick the bottom of each shell with a fork.

Bake for 10–12 minutes, until the shells look set and lightly golden at the edges. Cool completely before filling.

In a saucepan over medium heat, whisk together lemon juice, lemon zest, granulated sugar, and the 3 eggs. Stir constantly as it warms.

Cook until the mixture thickens noticeably (8–10 minutes). It should go from loose and foamy to glossy and creamy, coating the back of a spoon.

Remove from heat, whisk in the cubed butter until fully melted and smooth. Let cool slightly, then divide among the cooled tart shells. Chill for 1 hour.

Set a heatproof bowl over a pot of simmering water. Add the egg whites, sugar, and cream of tartar. Whisk until warm and sugar feels dissolved.

Beat until stiff peaks form and the meringue looks glossy. Mix in the vanilla extract and tint with violet food coloring until desired shade.

Pipe or spoon the meringue onto the chilled tarts. Torch until lightly golden on the ridges. Garnish with edible lilac flowers if desired.

Serve chilled for the best contrast between the cool curd and toasted meringue.