Preheat your oven to 350°F (175°C). Roll out the pie crust and fit it into a 9-inch pie plate, trimming any excess. Prick the bottom with a fork, then bake for 15-20 minutes or until golden brown. Allow the crust to cool completely.

In a medium saucepan over low to medium heat, combine the brown sugar and butter. Stir until melted and bubbly. Gradually whisk in the egg yolks and stir until the mixture thickens, about 10-15 minutes. Remove from heat and let cool slightly.

In a clean mixing bowl, beat the egg whites on medium speed until soft peaks form, about 2-3 minutes. Gradually add the granulated sugar while continuing to beat until glossy and stiff peaks form, about 6-8 minutes.

Pour the butterscotch filling into the cooled crust. Spread evenly, then spoon the meringue on top, creating peaks and swirls while sealing the edges.

Bake the pie at 350°F (175°C) for about 10-15 minutes, or until the meringue is golden brown. Watch closely to prevent burning.

Remove from the oven and cool at room temperature for at least 2 hours before serving, either chilled or at room temperature.