Step 1: Make the crust
Preheat oven to 350°F (175°C). In a medium bowl, mix graham cracker crumbs, sugar, and melted butter until the texture resembles wet sand. Press the mixture firmly into the bottom and up the sides of a 9-inch pie dish.

Step 2: Bake the crust
Bake the crust for 8–10 minutes, until golden and slightly firm. Remove from the oven and let cool slightly while you prepare the filling.

Step 3: Prepare the lemon filling
In a mixing bowl, whisk together sweetened condensed milk, egg yolks, lemon juice, and lemon zest until smooth and well combined.

Step 4: Make the raspberry swirl
In a small saucepan over medium heat, combine raspberries, sugar, cornstarch, and water. Cook for 3–5 minutes, stirring and breaking down the raspberries until the mixture thickens. Strain through a fine-mesh sieve to remove seeds, if desired.

Step 5: Fill the pie crust
Pour the lemon filling into the baked crust. Drop spoonfuls of the raspberry sauce over the top, then use a knife or toothpick to swirl it gently into the lemon layer, creating a marbled pattern.

Step 6: Bake the pie
Bake the pie at 350°F for 15–18 minutes, or until the center is set but still slightly jiggly. The filling will firm up as it cools.

Step 7: Chill and serve
Let the pie cool at room temperature for 30 minutes, then refrigerate for at least 4 hours (or overnight) until fully chilled. Top with whipped cream, lemon zest, or raspberries before serving.