Preheat oven to 350 degrees. Brush the inside of an 8 inch(6 cup) bundt pan or a 9 in. (8 cup) springform tube pan with margarine or oil or spray non-stick cooking spray. Set aside. In a small mixing bowl, stir together flour, baking powder and salt. In a large mixing bowl, beat margarine with electric beaters until softened and well blended. Gradually add sugar and beat until well blended. Gradually beat in eggs. Beat in lime zest and juice. Using a wooden spoon or rubber spatula, alternately stir the dry ingredients and buttermilk into the gg mixture, beginning and ending with the dry ingredients. Spoon the mixture into the pan and bake 35-50 minutes. Loosen dedges and invert onto a wire rack set over a plate. To make syrup: In a small bowl, whisk together the confectioner's sugar and lime juice. While the cake is still warm, poke holes in it using a skewer, cake tester or a fork. Slowly spoon the lime syrup over the cake. Cake can be made ahead and kept covered in refrigerator for up to 24 hrs. : 07/24/92 7:18 PM 345 calories per serving; 5 g protein, 10 g fat, 60 g carbohydrate, 259 mg sodium, 54 mg cholesterol