In a large microwave-safe bowl, combine flour, sugar, and egg yolks.
Gradually whisk in the milk until smooth.
Microwave the mixture one minute at a time, stirring thoroughly after each interval, until thick and creamy.
Stir in the butter, vanilla extract, and shredded coconut.
Pour the custard mixture into the pre-baked pie crust, spreading evenly.
Ensure your mixing bowl and whisk attachment are grease-free.
Using a stand mixer, beat the egg whites and cream of tartar until frothy.
Slowly add sugar, one tablespoon at a time, while continuing to whip until stiff peaks form.
Add vanilla extract and whip briefly to combine.
Spread the meringue evenly over the custard, ensuring it touches the edges of the crust to seal completely.
Bake in a preheated oven at 325°F–350°F until the meringue is golden brown, about 10–12 minutes.
Allow the pie to cool at room temperature for at least an hour before slicing.