Preheat the oven to 425°F (220°C).
Prepare the pie crust and place it in a 9-inch pie pan.
In a large mixing bowl, combine strawberries, rhubarb, sugar, flour, lemon juice, and cinnamon.
Let the fruit mixture sit for about 15 minutes to macerate.
Pour the macerated fruit mixture into the prepared pie crust and dot with butter.
Cover with a top crust or create a lattice design, sealing the edges.
Bake in the preheated oven for 15 minutes, then reduce to 350°F (175°C) and bake for an additional 30 minutes.
Remove from the oven and let cool for at least 1 hour before slicing.