Preheat the oven to 325 degrees F. Grease and flour 4 3x5 inch loaf pans.
With an electric mixer, beat the softened butter until creamy. Gradually add the sugar (⅓ cup at a time) beating well. Continue beating butter and sugar until fluffy.
Reduce speed to low and add 1 egg. Mix on low until egg is fully blended, then increase speed and beat for 30 seconds. Repeat with remaining eggs, adding individual eggs on low and increasing speed. Beat in the lemon paste and the salt.
Mix together the flour and the baking powder, then add to the batter and stir on low until fully blended.
Spoon batter into the pans and bake for about 45 minutes or until a tester inserted comes out clean.
Let cool in pans for 30 minutes, loosening it slightly from the sides while cooling.
To make glaze, combine sugar and lemon paste, then add water 1 teaspoon at a time, stirring until creamy and smooth. Drizzle over cake in pan. Allow the glaze to set somewhat, then remove from pan.
Notes
For best results, weigh the flour. If using White Lily you'll definitely want to weigh it as the volume may be a little different.