Preheat the oven to 325°F.
In a medium bowl, sift together flour, baking powder, and salt.
In a large bowl, beat butter and sugar with an electric mixer until light and fluffy.
Add the eggs, one at a time, beating well after each addition.
Add the sour cream and vanilla. Beat again to combine.
With the mixer on low, alternately add 1/3 of the flour mixture and 1/3 cup of the buttermilk. Beat just until combined Repeat this two more times, ending with the last 1/3 cup of buttermilk.
Grease a 10-inch angel food or Bundt cake pan.
Sprinkle the raw sugar into the greased cake pan, then gently tilt the pan back and forth and side to side to get the sugar to stick to the bottom and the sides of the pan.
Carefully arrange ½ cup of the toasted coconut over the sugar in an even layer around the bottom of the pan.
Pour the cake batter over the sugar coconut mixture. Do this carefully so that you don't disturb the sugar coconut mixture. Gently tap the cake pan on the counter to remove any air bubbles.
Bake the cake for 60-65 minutes or until a toothpick inserted in the center comes out clean. Remove the cake from the oven and allow the cake to cool in the pan for several hours.
Gently invert the cake onto a plate.