Requires 5-6 lemons. Preheat oven to 350 degrees F. Grease and flour 2 (8 1/2 x 4 1/4 x 2 1/2-inch) loaf pans, lining the bottom with parchment paper, if desired. Cream, using paddle attachment, butter and 2 cups granulated sugar in bowl of electric mixer until light and fluffy, approximately 5 minutes. With mixer on medium speed, add eggs, 1 at a time, and the lemon zest. Sift together flour, baking power, baking soda, and salt into bowl. In another bowl, combine 1/4 cup lemon juice, buttermilk, and vanilla. Alternately add flour and buttermilk to batter, beginning and ending with flour mixture. Divide batter evenly between pans, smoothing the tops. Bake 45 minutes - 1 hour, until tester comes out clean. When cakes are done, cool 10 minutes. Meanwhile combine 1/2 cup granulated sugar and 1/2 cup lemon juice in small saucepan, cooking over low heat until sugar dissolves. Remove cakes from pan and set on wire rack over jelly pan (best to set upside down on rack so that syrup is spooned onto the bottom of the cake as it will adsorb better than spooning over the top). Spoon lemon syrup over cakes, then allow cakes to cool completely. Glaze: Combine 2 cups sugar and 3 1/2 tablespoons fresh lemon juice in a bowl, mixing with whisk until smooth. Pour over the tops of the cakes and allow to drizzle down the sides.