Preheat oven to temperature specified on cake mix. Generously grease cake pans.
Add all ingredients for cake in a large mixing bowl and mix on low with stand or hand mixer just until blended, then on medium for 2 minutes.
Pour batter equally into the three cake pans. Bake for 30 minutes or until an inserted toothpick comes out clean. Remove from oven and cool for 5 minutes. Then, turn cakes out on cooling rack to cool completely.
Combine first 4 ingredients in large saucepan. Place on stovetop on low heat. Stirring constantly, melt butter and bring to a low boil. Cook while stirring for 12 minutes.
Remove from burner and add vanilla, 1/2 of coconut and 1/2 of pecans. Stir while cooling and frosting becomes thicker. Add rest of coconut and pecans. Mix well.
Place first round cake on cake stand or turntable. Generously spoon out 1/3 of the frosting on to the cake. Carefully spread to the edges. Repeat with the rest of the cakes. Use a spatula to smooth the sides of the frosting between the layers. Fill any gaps between the layers with any extra frosting. Left over frosting can be added to the top.
Cover and store any leftover cake at room temperature for 1 day or cover and store in the refrigerator for up to a week.