Preheat the oven to 350°F.
In a medium bowl, whisk together flour, baking powder, baking soda, and salt. Set aside.
In a large bowl, beat the butter and sugar together until light and fluffy, about 3-4 minutes.
Add eggs one at a time, beating well after each addition.
Mix in lemon zest and lemon juice. Gradually add the dry ingredients alternating with buttermilk, starting and ending with the dry ingredients.
Grease and line two 8½x4-inch loaf pans with parchment paper. Pour the batter into the prepared pans and smooth the top.
Bake for 60-70 minutes, or until a toothpick inserted into the center comes out clean. Be careful not to underbake, as it will make the loaves sink in the center.
Let the cake cool in the pan for 10 minutes, then turn out onto a wire rack to cool completely.
For the glaze, whisk together powdered sugar and lemon juice until smooth, adding more lemon juice if needed to reach your desired consistency.
Drizzle glaze over the cooled cakes.