Prepare yellow cake mix according to package directions for a 9 x 13" baking pan.
While cake is baking, stir together the pineapple and sugar in a small saucepan over medium heat.
Bring to a boil, stirring constantly, until the sugar is dissolved (about 2-3 minutes). Remove from heat and wait for cake to finish baking.
Once the cake is finished baking, while still hot, poke holes all over the top with a fork.
Pour the warm pineapple mixture over the cake.
Spread out the pineapple mixture so it evenly covers the cake.
Allow the cake to cool completely. Once cake is cooled, it's time to start the frosting!
In a large bowl, beat together the cream cheese and butter (using an electric or stand mixer) on medium speed until smooth, about 2 minutes.
Gradually add in the confectioner's sugar, beating until the frosting is smooth and creamy. (remember, if using a stand mixer, to occasionally scrape down the sides)
Finally, stir in the chopped pecans.
Drop the frosting by dollops onto the cake.
Smooth and spread it to coat.
Cover and refrigerate the cake until fully chilled before serving (2 hours).
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Notes
The cake will keep for up to 5 days when stored, covered, in the fridge.