Prepare the premade pie crust according to blind baking package directions and set aside.
Preheat the oven to 375 degrees F.
Whisk the cornstarch and sugar in a saucepan. Add the blood orange zest, blood orange juice, and lemon juice slowly, while stirring, over medium heat. Stir until thickened, about 4 minutes, then boil for one minute.
Portion a half a cup of the boiling mixture and add to your egg yolks slowly, stirring very quickly with a whisk so your eggs don't curdle.
Add the yolk mixture back to the pot with the sugar mixture. Boil one more minute over medium heat, stirring constantly. It should be fairly thick and starting to cling to the whisk.
Stir in butter and salt until butter is melted and pour the mixture into the blind-baked pie shell. Set aside while you prepare the meringue.
Beat the egg whites and cream of tartar in the bowl of a stand mixer on high speed until frothy. Slowly add sugar until meringue is thick and glossy.
Spread the meringue over the pie filling, sealing to the edges, and bake for 12-15 minutes until meringue is set. Set aside to cool.
Cool to room temperature and enjoy or chill for several hours, uncovered, and serve.