1. Preheat Oven:
   Preheat your oven to 325°F (163°C). If using a tart pan with a removable bottom, line the bottom with parchment paper.
2. Prepare the Crust:
   In a bowl, combine graham cracker crumbs, melted butter, brown sugar, and cinnamon (if using). Mix until the crumbs are evenly coated and hold together when pressed.
   • Ingredients: 1½ cups graham crackers, 6 tablespoons salted butter, ¼ cup brown sugar, ¼ teaspoon ground cinnamon
3. Form the Crust:
   Press the crust mixture into a 9-inch deep-dish pie pan, spreading it evenly across the bottom and up the sides. Use the bottom of a cup or jar to press firmly. Set aside.
4. Make the Filling:
   In a large mixing bowl, whisk together condensed milk, lemon zest, lemon juice, salt, and egg yolks until smooth.
   • Ingredients: 2 (14-oz.) cans sweetened condensed milk, 4 large egg yolks, 1 teaspoon lemon zest, juice of 5 medium lemons
5. Bake the Pie:
   Pour the filling into the prepared crust. Bake for 20 minutes, or until the filling is just set.
6. Chill:
   Cover the pie loosely with plastic wrap and refrigerate for at least 6 hours or overnight to allow the filling to firm up completely.
7. Prepare Whipped Cream (Optional):
   Combine cold heavy cream, vanilla, and powdered sugar in a mixing bowl or stand mixer. Whip on medium-high speed for about 3 minutes, or until soft peaks form.
   • Ingredients: 1 cup heavy cream, 3 tablespoons powdered sugar, ½ teaspoon pure vanilla extract
8. Serve:
   Slice the chilled pie and serve with a dollop of whipped cream, if desired.

Enjoy this refreshing and zesty dessert with family and friends!