Preheat the oven to 350 degrees F. (325 degrees F. if using a glass baking pan).
In a large mixing bowl, combine the cake mix ingredients using an electric mixer to beat the ingredients for 1 minute, scraping the bowl half way through. Meanwhile, in a medium mixing bowl, combine the topping ingredients and reserve.
Pour the prepared cake batter into a greased 9 x 13 pan. Sprinkle the prepared filling mixture over the batter, then use a butter knife to swirl the topping down into the batter a bit.
Bake the cake, uncovered, on the center rack of the preheated oven for 30-35 minutes, or until a cake tester or knife inserted into the center of the cake comes out clean.
While the cake is baking, combine the icing ingredients in a medium mixing bowl and whisk until smooth.
When the cake is removed from the oven, immediately pour the prepared icing over the hot cake, then cover the cake pan tightly with foil, letting the cake cool completely while covered.
To serve, cut the cooled cake into 12 pieces and serve. Cake can be reheated in the microwave if you'd prefer to eat it warm.
Notes
If you are using a glass baking dish to make this recipe, reduce the heat from 350 degrees F. to 325 degree F.
Covering the cake with foil after it's removed from the oven and frosting will ensure that the cooled cake turns out very very moist. In this case, the frosting also seals in heat and make the cake moist, too.
If you don't have chopped pecans on hand, you may substitute walnuts. Sometimes I leave out the nuts entirely (when I have picky sons bugging me) but this cake is definitely better with the nuts included.