Preheat oven to 350° F. Grease a 9x13-inch baking pan with non-stick spray. (Or you can line with parchment paper for easy removal).
In a large bowl, whisk the flour, sugar, baking powder and salt together. Add softened butter to flour mixture, stir with a spatula until combined.
In a medium bowl, whisk together the eggs, lemon juice and lemon zest. Pour mixture into the flour mixture. Stir with a spatula until smooth and combined. (A few lumps may remain).
Pour batter into prepared baking pan and spread out evenly. Bake 30 to 35 minutes or until a toothpick inserted in center comes out mostly clean. Remove from oven and allow to cool completely before glazing.