Preheat oven to 350 degrees. Line a 9 x 5-inch loaf pan with parchment paper. Allow paper to hang over the sides for easy removal
Place the butter in a large mixer bowl. Beat on medium 30 to 45 seconds or until creamy. Scrape down the sides of the bowl and push all the butter to the center of the bowl
Add the eggs, lemon juice and vanilla. Beat on low 10 seconds to combine. Increase speed to medium-low and beat about 30 seconds until fully combined. Scrape down the sides of the bowl
Sift in the dry ingredients until no lumps. If no sifter or mesh strainer place the dry ingredients in a separate bowl and whisk the dry ingredients until there are no lumps
Beat the dry ingredients into the wet ingredients on low about 10 seconds to moisten the dry ingredients. Increase the speed to medium and beat 30 to 45 seconds until a smooth dough has formed. Scrape down the sides of the bowl
Form the dough into a smooth ball. Massage for about 1 minute to absorb extra moisture. Place dough into prepared loaf pan and press evenly throughout the pan
Place in preheated oven and bake at 350 degrees for 20 to 25 minutes or until golden. Remove from the oven. Cool in pan about 30 minutes or until firm. Grasp over hanging paper and transfer slab to a wire rack. Allow to cool completely before cutting into desired size bars.
If desired once cooled frost or glaze the slab before cutting into bars. Another option is as soon as the slab is transferred to a wire rack sprinkle with the desired amount of powdered sweetener then allow to cool completely before cutting into desired size bars. Store leftovers in an airtight container at room temperature up to 1 week