Preheat oven to 350 degrees. Set aside an ungreased 13 x 9 inch baking pan.
Place the cake mix, melted butter and egg in large mixing bowl, blend with electric mixer on low for 2 minutes. Scrape sides several times. Will come together for a thick dough. Press the crust mixture evenly over the bottom and 1/2 inch up the sides of the pan, smoothing it out.
Bake the crust until it begins to brown 20 minutes. Remove from oven and set aside.
Meanwhile prepare the filling. Place corn syrup, brown sugar, eggs, and vanilly in same mixing bowl used to prepare crust, blend with an electric mixer on medium speed until well combined, 1 minute. Scrape sides of bowl and fold in pecans until well distributed.
Pour the filling over the baked crust and spread with the spatula so that the filling covers the entire surface. Return pan to oven.
Bake the bars until the crust is golden brown and the filling just starts to set, 22-25 minutes. Remove from oven and place on rack to cool for 30 minutes.
Cut into 24 bars and serve. Bars may be frozen for up to 6 months. Thaw overnight in refrigerator before serving.