Preheat the oven to 400 degrees F ( 200 degrees C ). Coat a 15x10x1-inch jelly roll pan with nonstick spray.

Combine brown sugar and eggs in a heavy saucepan; cook over medium heat, stirring constantly, until sugar is dissolved. Remove from heat. Stir in flour, pecans, vanilla, and salt until well combined; transfer mixture to the prepared pan.

Bake in the preheated oven for 15 minutes. Cool completely on a wire rack, then cut into 36 squares.