A delightful strawberry rhubarb pie filling balancing sweet strawberries with tart rhubarb, thickened to perfection with lemon and vanilla accents.
3 cups rhubarb, sliced into 1/2-inch pieces
2 3/4 cups strawberries, chopped
1/3 cup granulated sugar
1/3 cup packed brown sugar
1/4 cup cornstarch
1/4 teaspoon salt
1 teaspoon vanilla extract
2 tablespoons lemon juice
1 tablespoon salted butter