Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans or one 9x13-inch pan.
In a medium bowl, cream together white sugar and 1/2 cup of unsalted butter. Mix in eggs and 3 mashed bananas.
Sift together flour and baking soda in a separate bowl.
Add the flour mixture to the creamed mixture alternately with buttermilk, mixing well after each addition.
Blend in 1 teaspoon of vanilla extract. Fold in 1 cup of chopped pecans and 1 cup of shredded coconut.
Pour the batter into prepared pans.Bake in the preheated oven until a tester inserted in the center comes out clean, about 45 minutes.Cool completely on wire racks.