Preheat the oven to 325° F. Line the bottom of an 8x8" pan with parchment paper. Make sure the paper hangs over the sides so you can pull up the bars from the pan later, making it easier to cut the bars.
In your stand mixer with a paddle attachment mix together the sugar, flour, and salt until thoroughly mixed. Add in the butter and vanilla and mix. It will be thick and crumbly. Press into the pan using a bottom of a measuring cup or flat-bottomed drinking glass. You want this to be packed in tight and even.
Prick with fork about 10-15 times across the crust. Bake for 16-18 mins should not be browned yet.
Make the filling while the crust bakes. In a large bowl or stand mixer, sift together your flour and sugar. Then in whisk the eggs, lemon juice and zest, and whisk until smooth.
Pour the lemon mixture over warm crust and bake for another 20-22 mins, the middle should no longer jiggle (maybe just the slightest of jiggles).
Remove from oven and let cool at room temperature, about 1-2 hours.
When the bars are cooled, you can move them to the refrigerator another 1-2 hours until chilled.
Once they are completely chilled, you will lift from the parchment paper and put bars on a cutting surface. Cut into squares (or rectangles or triangles). Sift powdered sugar on top or even add lemon slices for decoration.
Notes
- Stand Mixer: I make my dough from scratch and I use a stand mixer with a paddle attachment. You could do this with a handheld mixer or even potentially a food processor or blender.- Bake Time: Now, this is the difference of a very gooey top or set top. You 100% need to be keeping your eyes on the oven to make sure they don't overcook. But again, if they brown a little, no worries, you can coat in powdered sugar! It may jiggle just the slightest and that's okay.- Cooling: You definitely need to cool them outside the fridge first for at least 1 hour. Then move to the fridge for about 1-2 hours to chill. I personally love to keep mine in the fridge so they are nice and cool when I go to eat them! I serve them chilled and keep them in the refrigerator for up to one week. Or you can keep or serve them at room temp, but only for about 2-3 days.