Preheat your oven to 350°F (175°C). In a mixing bowl, combine flour, half of the sugar, salt, and the cold butter. Use a pastry cutter or fork to cut the butter into the dry ingredients until the mixture resembles coarse crumbs. Press two-thirds of this mixture evenly into the bottom of your prepared baking pan to form the crust.
In another bowl, gently toss the sliced strawberries with lemon zest, lemon juice, remaining sugar, and cornstarch until well coated. Spread this strawberry mixture evenly over the baked crust, distributing slices to fill the pan.
Bake the layered crust and filling for about 15 minutes or until the filling begins to bubble and the strawberries are tender.
While the filling bakes, combine the remaining crumb mixture with any remaining flour and sugar to create the crumb topping. Use your fingers or a fork to crumble it evenly over the bubbling filling.
Return the pan to the oven and bake for an additional 20 minutes, or until the topping is golden brown and crunchy.
Remove the pan from the oven and let the bars cool slightly—about 15 minutes—so they set up and become easier to slice. You should see a vibrant, bubbling fruit layer encased in a crispy, crumbly topping.
Pick up your spatula or a sharp knife and cut the bars into squares or rectangles. Serve warm or at room temperature for a delightful tangy-sweet dessert with a crunchy topping and tender fruit filling.
