Preheat the oven to 350°F (175°C). Line the baking pan with parchment paper for easy removal.
In a mixing bowl, combine 1 cup of flour, 1/2 cup sugar, and the cold, cubed butter. Use a pastry cutter or forks to cut in the butter until the mixture resembles coarse crumbs with some larger pea-sized chunks. Set aside for the topping.
1 1/2 cups all-purpose flour
In another bowl, toss the sliced strawberries with 1/4 cup sugar, lemon zest, and cornstarch until evenly coated. The mixture should start to thicken slightly and look shiny.
1 1/2 cups all-purpose flour
Spread the strawberry filling evenly into the prepared baking pan, creating a smooth layer.
1 1/2 cups all-purpose flour
Sprinkle the crumbly topping evenly over the strawberry layer, ensuring full coverage to create a crust-like top.
1 1/2 cups all-purpose flour
Bake in the preheated oven for 35 minutes, or until the topping is golden brown and the filling is bubbling around the edges. The top should be crisp and fragrant.