Preheat oven to 350 degree F. Grease and flour a 9-inch springform pan; set aside. For mango sauce, in a medium saucepan stir together the 1/4 cup sugar and the cornstarch. Stir in the orange juice and chopped mango. Cook and stir over medium heat until thickened and bubbly. Set aside to cool slightly.
For crust, in a large mixing bowl stir together the flour and 3/4 cup sugar. Using a pastry blender, cut in butter until mixture resembles coarse crumbs. Remove 1 cup of the crumb mixture and set aside. Stir baking powder and baking soda into remaining crumbs in bowl. In a small bowl stir together the sour cream, 1 egg, and vanilla until combined. Stir into flour mixture in bowl until moistened. Using moistened fingers, spread mixture into the bottom and 1 1/2 inches up the sides of the prepared pan; set aside.
For filling, in a medium mixing bowl beat cream cheese and 1/4 cup sugar with an electric mixer until combined. Add 1 egg and beat just until combined. Spoon into crust-lined pan. Spoon the mango sauce on top of the cream cheese layer. Sprinkle with the 1 cup reserved crumb mixture; sprinkle with macadamia nuts.
Place pan in a 15x10x1-inch baking pan. Bake for 45 minutes or until top and edges of crust are golden. Cool in pan on a wire rack for 15 minutes. Loosen crust from sides of pan. Cool 30 minutes more. Remove sides of the pan; cool coffee cake completely. Cover and chill at least 4 hours or overnight. Serve chilled or at room temperature. Makes 12 servings.