For cake: Combine all ingredients in a large mixing bowl; whisk till well combined.
Pour batter into a greased 9x13" pan and bake in an oven preheated to 350° for about 35 minutes or till a toothpick inserted in the middle comes out clean.
While cake is baking, prepare frosting: Combine butter, sugar, and evaporated milk in a saucepan. Bring to a boil; cook and stir over medium heat until thickened, about 5 minutes. Remove from heat and stir in vanilla, salt, pecans, and coconut.
Poke holes in the hot cake with the top of a wooden spoon. Spread the frosting evenly over the hot cake.
Let cake cool for a few minutes before serving. Can be served warm or at room temperature.