Preheat oven to 350°F (175°C).
Whisk pumpkin puree, brown sugar, eggs, cream, milk, spices, vanilla, and salt until smooth.
Pour filling into prepared crust and bake 45–50 minutes until set.
Cool pie completely before adding topping.
Beat egg whites and cream of tartar until soft peaks form.
Gradually add sugar while beating until stiff glossy peaks form.
Spread meringue over cooled pie, sealing edges.
Toast meringue with a kitchen torch or broil briefly until golden.
Chill slightly before slicing and serving.