This recipe is so easy and came from a magazine. When I fixed it the first time for a family Sunday dinner, my grandson told me that I had to fix it the next Sunday too. You have to refrigerate the cake at least four hours but I think its best when left overnight so I always make it the day before I need it.
Preheat oven to 350 degrees. Spray a 13 x 9 inch pan with baking spray with flour. In a large bowl, prepare cake mix according to package directions, adding 1 cup chopped pecans. Spoon batter into prepared baking pan and bake for 18 to 20 minutes or until tests done. Let cool in pan 10 minutes.
Using the end of a wooden spoon, poke 1/2 inch deep holes in cake at 1" intervals. In a medium bowl, whisk pudding mix and milk until slightly thickened, about two minutes. Stir in pineapple. Pour mixture evenly over cake. Cover and refrigerate at least four hours or up to 3 days. Spread whipped topping over cake and sprinkle with chopped pecans before serving. Store in refrigerator.