Preheat the oven to 350°F (175°C). Grease and flour three 9-inch round pans, tapping out excess flour.

In a large bowl, beat the butter with both sugars on medium speed until light and fluffy, about 3–4 minutes.

Add the eggs one at a time, beating well after each addition so the batter stays emulsified.

Stir in the buttermilk and vanilla until combined, scraping the bowl so nothing sticks to the sides.

In another bowl, sift together flour, cocoa powder, baking soda, and salt.

Add the dry mixture to the wet in three additions, mixing on low speed and stopping as soon as the batter is uniform. Avoid overmixing.

Fold in the shredded coconut and chopped pecans by hand with a spatula.

Divide the batter evenly among the prepared pans and smooth the tops with an offset spatula.

Bake for 25–30 minutes, rotating once halfway through. A toothpick inserted in the center should come out clean or with a few moist crumbs.

Cool the cakes in the pans for 10 minutes, then invert onto wire racks and cool completely.

Frost with a chocolate frosting or a coconut-pecan frosting. Garnish with extra coconut and pecans if desired.