On a parchment-lined baking sheet, toast unsweetened shredded coconut in 350 degree oven for 4 min. Keep an eye on it! It can burn fast. Remove from oven and let cool.
Add sugar, flour, eggs, baking soda, vanilla, and crushed undrained pineapple to a large bowl and mix with a spoon. The mixture will be lumpy because of the pineapple chunks, but make sure it’s well-mixed.
Spread into a 9x13 baking dish that has been greased with cooking spray. Bake for 35-40 min in 350 degree oven. Remove cake from oven when a toothpick inserted in the center comes out clean. Let it cool on the counter.
In a smaller mixing bowl, combine room temperature butter and sweetened condensed milk and whip with hand mixer on medium speed for at least 8 minutes or until creamy and smooth.
Spread the frosting on the cake. It’s ok if the cake is not fully cooled before frosting for this recipe! The frosting melts into the cake making it extra moist and delicious.
Top with the toasted coconut, and then add chopped pecans. Enjoy your cake cold or warm!