Preheat your oven to 350°F (175°C). Grease a 9x13-inch baking pan or line it with parchment paper, leaving an overhang for easy removal.
In a large bowl, whisk together 2 cups all-purpose flour, 1/2 cup granulated sugar, and 1/4 teaspoon salt. Add 1 cup cold unsalted butter pieces and cut into the dry ingredients with a pastry blender or fingertips until the mixture resembles coarse crumbs.
Press the crust mixture evenly into the bottom of the prepared pan. Bake for 15 minutes, or until lightly golden.
While the crust bakes, melt 1/2 cup unsalted butter in a medium saucepan over medium heat. Stir in 1 cup packed light brown sugar and 1 cup light corn syrup. Bring to a gentle simmer, stirring occasionally, then remove from heat and let cool for 5 minutes.
In a separate bowl, lightly whisk 3 large eggs. Slowly pour the slightly cooled sugar mixture into the eggs, whisking constantly. Stir in 1 teaspoon vanilla extract and 1/4 teaspoon salt, then fold in 2 cups pecan halves.
Pour the pecan filling evenly over the warm crust and return the pan to the oven. Bake for 25–30 minutes, or until the filling is set and lightly golden (center should not wobble).
Let the bars cool completely in the pan on a wire rack (about 2 hours). Use the parchment overhang to lift out the slab, then place on a cutting board and slice into bars.