Preheat the to 350°F. Line an 8X8 inch baking pan with aluminum foil, extending the edges of the foil on one side, 2 inches. Rotate the pan and line it with a second sheet of aluminum foil perpendicular to the first, extending the edges of the foil 2 inches on the other ends. Spray the foil with nonstick cooking spray.
In the work bowl of a food processor, add the flour, brown sugar, pecans, salt, and baking powder. Pulse ingredients about 5 times or until the mixture looks like coarse sand. Add the butter and pulse again about 8-10 times. Pour mixture into prepared baking pan and press in evenly. Bake in the preheated oven until the crust begins to brown, about 20 minutes.
Make the filling:
In a medium mixing bowl, mix together brown sugar, melted butter, corn syrup, bourbon, vanilla, and salt until just combined. Whisk in the egg just until incorporated.
Pour the filling mixture over the hot crust and then top evenly with pecans.
Bake until the top forms cracks and is brown, 22-25 minutes. Cool on wire rack completely. Cut into bars.
Toast the pecans: Toast them all at the same time on a rimmed baking sheet in a 350-degree oven for about 8 minutes before you begin making the bars.