Preheat oven to 400 degrees F (200 degrees C). Press 1 pie crust into a 9-inch pie dish.
Stir tomatillos, strawberries, tapioca, sugar, and lemon juice together in a bowl; let stand, stirring occasionally, until sugar is dissolved, about 15 minutes. Spoon tomatillo-strawberry mixture into the prepared pie crust. Scatter butter slices over filling.
Cover pie with second pie crust and pinch edges together to seal. Cut slits into top crust for ventilation. Place pie on a baking sheet.
Bake in the preheated oven until top crust is golden brown and filling is bubbling, about 50 minutes.