Arrange an oven rack in the lower-middle portion of the oven, then heat the oven to 350°F (175°C). This placement encourages even baking while helping protect the pastry from excessive browning.

If the eggs are still refrigerated, bring them to room temperature so they will combine more readily with the remaining filling ingredients.

Coarsely chop the 2 1/2 cups of pecans, leaving a mixture of smaller pieces and larger chunks to provide varied texture throughout the finished pie.

Set the unbaked 9-inch pastry shell on a baking sheet. The sheet provides additional stability during handling and will catch any filling that may drip while baking.

Place the 3 room-temperature eggs, 1 cup corn syrup, 3/4 cup packed brown sugar, 3 tablespoons melted and cooled unsalted butter, 1 teaspoon vanilla extract, 1 teaspoon cinnamon, and 1/2 teaspoon salt in a medium mixing bowl.

Whisk the mixture energetically for approximately 1–2 minutes, continuing until the brown sugar has dissolved thoroughly and the filling appears smooth and evenly blended. Proper mixing helps prevent a grainy finished texture.

Continue until the eggs and melted butter are fully incorporated into a cohesive custard mixture. This emulsification contributes to the pie's smooth consistency and helps distribute the pecans through the filling during baking.

Distribute the chopped pecans in an even layer over the base of the prepared pastry shell.

Gradually pour the custard mixture over the pecans, filling the shell nearly to the top. Depending on the depth of the crust, a very small amount of filling may remain.

Transfer the assembled pie immediately to the preheated 350°F (175°C) oven, keeping it on the lower-middle rack. Bake for 55–60 minutes, or until the outer portion of the filling is set while the very center retains a slight jiggle. The remaining heat will continue setting the custard after the pie leaves the oven, helping prevent an overly firm or rubbery texture.

Remove the baked pie from the oven and leave it on the baking sheet to cool at room temperature for a minimum of 2 hours before cutting.

During this cooling period, the custard will continue to firm and stabilize. Slicing the pie while it is still warm may cause the filling to lose its shape.