1. Combine cake mix, butter and 1 egg for the crust. Measure out 2/3 cup of this mixture and set aside. Pat remaining crust mixture into the bottom of a 13 x 9 pan, lightly sprayed with cooking spray.
2. Bake at 350 for 15 minutes.
3. While crust is baking, beat reserved crust mixture, remaining 3 eggs, corn syrup, sugar and vanilla until well combined.
4. Stir in pecans.
5. Pour over the baked crust. Increase oven to 375 and bake for 30 minutes or until set.
6. Let cool before cutting into bars.
7. Lightly sprinkle with confectioner's sugar just before serving, if desired.