You'll need a 10" tube pan (angel food cake pan) for this coffee cake.
For the cake:
3/4 cup butter (1 1/2 sticks)
1 1/4 cups sugar
2 1/2 cups flour
2 tsps baking powder
1 tsp baking soda
1/2 tsp salt
1 1/2 cups sour cream
2 tsps grated orange zest (optional)
For the streusel:
1/4 cup flour
1/4 cup butter
1/2 cup sugar
1 cup chopped macadamia nuts (unsalted, if possible, or just rinse salt off. I've also left the salt on occasionally and it doesn't seem to affect the outcome.)
1 1/4 cups shredded coconut, toasted for 5-10 minutes in a 375 degree oven. (Watch closely! It has never taken 10 minutes for my coconut to toast.)
Grease the tube pan and dust lightly with flour. Or just spray with Pam.
In a large mixing bowl, cream the butter with the sugar until fluffy. Beat in the eggs. Stir together the flour, baking powder, baking soda and salt. Add this mixture to the butter/sugar/eggs mixture. Blend thoroughly but don't beat hard. Stir in the sour cream and orange zest (I use a low setting on the stand mixer for this.).
Cream together the flour, butter and sugar for the streusel. Mix in nuts and coconut.
Spread half the butter in the tube pan. Sprinkle half the streusel on top. Add the rest of the batter and sprinkle the remaining streusel. Bake in a 350 degree oven for about 50 minutes or until a cake tester comes out clean. Baking time will vary, depending on your oven, so watch closely and check early.
Cool the coffee cake thoroughly on a rack and carefully remove from pan. Enjoy!