Preheat oven to 325 degrees.
Lightly oil a 9x5 inch loaf pan.
Combine the flour,baking powder,salt,lemon zest and rosemary in a medium bowl; stir to blend.
In a large bowl or electric mixer, beat the oil and sugar until well-blended; add the eggs one at a time, beating well after each addition until mixture is pale yellow.
Gradually add the flour mixture to the egg mixture, stirring to blend, also adding the buttermilk gradually until all cake ingredients are well-blended.
Spread mixture in the prepared pan.
Bake until bread is golden and sides begin to pull away from the pan, approximately 50-55 minutes.
To make the glaze: in a medium bowl,stir the confectioner's sugar and lemon juice until smooth; spread on the warm loaf.
Once the bread is thoroughly cooled, use a knife to loosen the sides of the bread from the pan and turn out.
Serve in slices.