Cream Filled Yellow Cake is a moist bundt cake that is filled with a marshmallow and whipped topping filling to remind you of a Twinkie.
Preheat oven to 350°F. Prepare a large bundt pan with butter and flour or by spraying with non-stick cooking spray.
In a large bowl, combine the cake mix, eggs, water, and oil. Mix until well blended (a few lumps are okay).
Pour batter into prepared bundt pan. Bake for 25-35 minutes, making sure to not overcook. As soon as an inserted toothpick comes out clean, remove it from the oven and let cool completely in the pan.
Once the cake has cooled completely (still in the pan), use a handle of a wooden spoon to make holes. Get almost all the way to the bottom (which will be the top of the cake once inverted). Every ½ inch, poke another hole, continuing around the entire cake. Make sure the holes are wide enough to hold the marshmallow and whipped topping filling.
In a small bowl, mix together the marshmallow fluff and whipped topping.
Place the filling in a piping bag fitted with a tip. (You could also use a zipped plastic bag with a corner tip cut off.) Pipe the filling into each hole of the cake. Be sure to get the filling as far down each hole as possible.
Carefully invert the cake onto a large plate or serving platter. Top with confectioners' sugar before cutting and serving.