1. Preheat oven to 350°. Line bottom and sides of a 13- x 9-inch pan with heavy-duty aluminum foil, allowing 2 inches to extend over sides; lightly grease foil.
2. Stir together 1 3/4 cups flour and 1/2 cup sugar. Cut in butter with a pastry blender or fork until crumbly. Press mixture onto bottom of prepared pan.
3. Bake at 350° for 20 to 23 minutes or until lightly browned.
4. Meanwhile, whisk eggs in a medium bowl until smooth; whisk in coconut, next 3 ingredients, and remaining 1 1/2 cups sugar. Stir together baking powder, salt, and remaining 1/4 cup flour; whisk into egg mixture. Pour over hot crust.
5. Bake at 350° for 25 minutes or until filling is set. Let cool 1 hour on a wire rack. Lift from pan, using foil sides as handles. Remove foil, and cut into bars. Garnish, if desired.