1. Preheat oven to 350 degrees F. Spray a bundt or tube pan with vegetable cooking spray, then dust with flour.
2. Place 3 of the lemons in a medium saucepan and cover with water. Bring to a boil, then reduce heat, cover, and simmer for 30 minutes. Drain and halve each lemon. Cool in a medium bowl about 20 minutes, remove the seeds, and pull off the stems. Process the lemons until smooth in a food processor or blender. Alternatively, return lemons to the bowl and puree with an immersion blender. Set 1 cup of the pureed lemon aside. (Reserve any extra for another use.)
3. While lemons cook, grate 1 Tbsp. zest from remaining 2 lemons, then halve and juice the lemons. Strain out pulp and measure 6 Tbsp. juice.
4. In a large bowl, whisk the 2 1/2 cups flour, baking powder, baking soda, and salt.
5. In a second large bowl, use an electric mixer on high speed to cream butter. Gradually add sugar and continue beating until light and fluffy, about 2 to 3 minutes. Add eggs, one at a time, beating until fully incorporated. Add vanilla, 4 Tbsp. of the lemon juice, lemon zest, and lemon puree and beat until smooth.
6. Add half the flour mixture and beat until smooth on low speed, then add remaining flour and beat until smooth. Stir in walnuts by hand.
7. Pour batter into prepared pan. Bake until lightly golden on top and a toothpick inserted in the center comes out clean, about 33 to 38 minutes.
8. Cool cake in pan for 10 minutes, then cool on a wire rack about 11/2 hours.
9. Prepare the icing. In a small bowl, stir together confectioners' sugar and remaining 2 Tbsp. juice. Drizzle half over cake. Let set for a few minutes, then drizzle remaining icing. To serve, cut into slices and garnish with lemon slices if desired.
Source: Hannaford fresh Magazine, January - February 2015