Preheat the oven to 425°F.
Roll out the pie crust and gently place it into a 9-inch deep-dish pie plate. Trim any excess dough hanging over the edges. Flute or crimp the edges, if desired. Place the pie crust in the refrigerator to chill while you prepare the filling.
In a large bowl, combine pumpkin, sweetened condensed milk, eggs, pumpkin pie spice, cinnamon, and salt. Whisk until the mixture is smooth and fully combined.
Pour the pumpkin filling into the prepared crust and smooth out the top with a spatula if needed.
Place the pie on the center rack of the oven and bake for 15 minutes.
Without opening the oven door, reduce the oven temperature to 350°F. Continue baking for an additional 35 to 40 minutes, or until a toothpick inserted into the center of the pie comes out clean.
Remove the pie from the oven and let it cool at room temperature before slicing and serving.
Top with whipped topping if desired.