Begin by preparing your strawberries and rhubarb. Wash them thoroughly, hull the strawberries, and slice them into bite-sized pieces. Chop the rhubarb, removing any tough ends.

In a large mixing bowl, combine the sliced strawberries and chopped rhubarb. Add sugar, cornstarch, vanilla extract, lemon juice, and salt. Gently stir until all the fruits are well coated in the mixture.

In a medium saucepan over medium heat, pour in the fruit mixture. Stir frequently until the ingredients begin to bubble. This should take about 5-10 minutes. You’ll notice the filling thickening as the sugars and cornstarch activate.

Once the mixture reaches a bubbly consistency, remove it from the heat and allow it to cool slightly before pouring it into your prepared pie crust or using it in another dessert.

If you’re making a pie, cover it with a top crust and bake according to your pie crust's instructions. If you’re just using the filling for other treats, go ahead and serve it straight up or with your favorite topping.