Preheat the oven to 425 degrees F (220 degrees C).

Mix raspberries, sugar, cornstarch, tapioca, and water together in a bowl; set aside as you arrange crust.

Line the bottom and sides of a 9-inch pie plate with one pie crust.

Spoon raspberry mixture into bottom crust, and put four 1 tablespoon pats of butter on top. Put on top crust and crimp edges. Make slits in the crust to allow the steam to escape.

Bake in the preheated oven for 15 minutes. Reduce heat to 350 degrees F (175 degrees C) and bake until crust is golden and fruit is bubbly, about 45 minutes more.