Preheat oven to 350°F. Coat a 9-inch pie plate with cooking spray; set aside. Gather all ingredients.
Beat egg whites and cream of tartar with a stand mixer fitted with a whisk attachment on medium speed until frothy, 30 seconds to 1 minute; continue beating until soft peaks form, 1 to 2 minutes more. With mixer running on medium speed, gradually stream in granulated sugar, about 2 tablespoons at a time, beating until well incorporated between each addition, about 4 minutes total. Increase mixer speed to medium-high, and beat until glossy, stiff peaks form, 4 to 5 minutes.
Fold graham cracker crumbs, pecans, baking powder, vanilla, and salt into mixture in mixer until evenly dispersed.
Spoon mixture into prepared pie plate; spread into an even layer. Bake in preheated oven until puffed and set, about 30 minutes. Let cool completely on a wire rack, about 3 hours. (Pie will deflate as it cools.)
To serve, beat cream, powdered sugar, honey, and rum in a large bowl with an electric mixer on medium speed until medium-stiff peaks form, 2 to 3 minutes. Spoon whipped cream over cooled pie; garnish with additional pecans and graham cracker crumbs.
