Preheat your oven to 350°F (175°C). Grease an 8x8 inch baking dish with butter or line it with parchment paper.

In a medium-sized mixing bowl, cream together the softened butter and sugar until light and fluffy. Stir in the vanilla extract, then gradually add the flour and a pinch of salt, mixing until a soft dough forms.

Reserve about 1 cup of the crust mixture for the topping. Press the remaining mixture evenly into the bottom of your prepared baking dish. Bake for about 15 minutes or until lightly golden.

In another bowl, combine the chopped strawberries, rhubarb, sugar, cornstarch, lemon juice, and salt. Stir until well combined.

Once the crust is ready, pour the filling mixture over it, spreading it evenly. Crumble the reserved crust mixture on top of the filling.

Bake for an additional 30-35 minutes until the topping is golden and the filling is bubbling.

Allow the bars to cool in the pan for about 30 minutes, then cut into squares. Serve warm or chilled!