Preheat your oven to 425°F (220°C).
In a medium bowl, combine the fresh raspberries, granulated sugar, cornstarch, lemon juice, and vanilla extract. Gently toss until the raspberries are well coated.
Pour the raspberry mixture into the pre-made pie crust, spreading it evenly.
Bake in the preheated oven for 15 minutes. Then, reduce the temperature to 350°F (175°C) and continue baking for an additional 25-30 minutes, or until the filling is bubbly and the crust is golden brown.
Remove the pie from the oven and let it cool completely on a wire rack. This will help the filling set properly.
Serve chilled or at room temperature, topped with whipped cream if desired.