• Preheat the oven to 325°F. Butter and flour a 9x5-inch loaf pan.

PREPARE THE CAKE:

• In a large bowl, use an electric mixer to cream the butter until smooth. Gradually add the sugar, and beat until light and fluffy, 4 to 5 minutes. Add the eggs, one at a time, beating well after each addition; beat in the lemon and lime zest.
• Sift together the flour, salt and baking powder. Gradually add the dry ingredients to the butter mixture in 4 to 5 additions, beat on low speed until just blended after each addition.
• Spoon the batter into the prepared pan. Bake for 1 hour and 15 minutes, or until a tester inserted into the middle comes out clean and the edges start to pull away from the sides of the pan. Let the cake cool in the pan on a rack while you prepare the glaze.

PREPARE THE GLAZE:

• In a small saucepan, combine the glaze ingredients. Cook over medium heat, stirring until the sugar dissolves- 1 to 2 minutes. Don't boil. Remove the glaze from heat.
• Remove the cake from the pan and set it on a rack over a sheet of wax paper. Brush the warm cake with the hot citrus glaze all over. Let it cool completely. Wrap the cake in plastic wrap and then wrap with foil. This cake is better when eaten the next day!