Preheat oven to 325 F and prepare the 9 X 13 pan with parchment paper. (Make sure to leave an overhang of parchment to make it easier to get the bars out of the pan)
Before beginning the crust, get your sugar and lemon zest and mix the zest into the sugar with your hands. You will perfume the sugar with the beautiful lemon flavor
Crust: To make the crust melt the butter, and when melted, mix with lemon sugar, salt, and vanilla. When all combined, add flour until a dough is formed.
Press the dough into the prepared 9 X 13 pan and bake for 20 - 22 minutes or until lightly browned.
While crust is in the oven make the filling
Filling: To make the filling whisk lemon juice with 6 eggs, set aside
In a different bowl, whisk together the lemon sugar and the flour (about 1 minute to break up any flour clumps)
Add the juice and eggs into the flour and sugar and whisk until combined.
When crust is removed from the oven, quickly poke holes in the crust (not all the way down) using a fork to allow the filling to soak into the crust.
Pour the filling over the crust and bake for 22 - 28 minutes until the center is mostly set and is no longer jiggly.
Cool for 2 hours at room temperature and then transfer to the fridge for another 1 - 2 hours.
Once cooled, run your knife along the edges to separate the bars from the pan, then lift the parchment paper out of the pan and cut into into squares, and top with powdered sugar.
They will last in the fridge for up to a week, or frozen for 3 - 4 months....If they last that long!