Chocolate-Coconut Pound Cake

Preheat oven to 325 °F. Butter an 8x4" loaf pan; line with parchment paper, leaving a generous overhang on long sides. Whisk flour, cocoa powder, salt, and baking powder in a medium bowl; set aside. Using an electric mixer on medium-high speed, beat oil, 1/4 cup butter, and 1 1/2 cups sugar until pale and fluffy, 5 –7 minutes. Add eggs one at a time, beating to blend between additions; beat until mixture is very light and doubled in volume, 5 –8 minutes. Add vanilla. Reduce mixer speed to low and add dry ingredients in 3 additions, alternating with buttermilk in 2 additions, beginning and ending with dry ingredients (do not overmix; it will cause cake to buckle and split). Scrape batter into prepared pan and run a spatula through the center, creating a canal. Sprinkle with coconut and remaining 1 tablespoon sugar. Bake cake, tenting with foil if coconut browns too much before cake is done (it should be very dark and toasted), until a tester inserted into the center comes out clean, 70 –80 minutes. Transfer pan to a wire rack; let cake cool in pan 20 minutes before turning out. DO AHEAD: Cake can be baked 5 days ahead. Keep tightly wrapped at room temperature.