
Mix cornstarch and lemon juice, warm blueberries and sugar over medium heat for 3 minutes, add cornstarch mixture, cook for 2 minutes, set aside.
Preheat oven to 350°F (177°C). Mix melted butter, sugar, vanilla, and salt, add flour, press into tart pan, and bake for 15 minutes.
Poke holes in warm crust, whisk filling ingredients, pour into crust, drop blueberry sauce and swirl, bake for 17-19 minutes.
Cool completely, chill for at least 2 hours before serving, garnish as desired.