Prepare cake in 9x13 in pan and bake as directed.
While 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, 2-3 min. Remove from heat and wait on the cake to finish baking. While cake is still hot, poke holes all over the top with a fork. Pour the warm pineapple mixture over the cake, spreading with spatula. Let cool.
In a large bowl, beat together the cream cheese and butter with electric mixer on medium speed until smooth, 2 min. Gradually add the confectioners' sugar, beating until the frosting is smooth and creamy. Add the pecans and mix well. Drop the frosting by dollops onto the cake until the top is mostly covered, them smooth and spread it to coat. Cover and refrigerate for 2 hrs until fully chilled before serving. The cake will keep for up to 5 days when stored, covered, in the fridge.