Who knows why it happened, but I got on a Lemon Bar jones and made three different batches in three days. This is the final recipe although they were all good.
I have actually included two different tops, because my wife sometimes prefers the cheese cakey one, while I go for the classic. So when you get to the recipe below, pick one or the other of the toppings...not both (although that might be an interesting experiment for another day).
Lemon Bars are part cookie, part pie. The bottom part is basically a cookie and the top part is like lemon pie filling, but a little thicker so it doesn't run. And the process reflects this two part nature.
Cookie Bottom
Classic Lemon Top make either this one
Cheesy Lemon Top or make this one
Preheat the oven to 350. Line an 8X8 inch pan with either aluminum foil or parchment paper. Spray with vegetable or baking spray.
In a food processor, pulse the flour, powdered sugar and salt. Chop the butter up into reasonable chunks, then pulse until it is distributed evenly in the flour mix. Press the mix evenly into the bottom of the pan. This is most easily done with the bottom of a metal measuring cup or a drinking glass. Bake for 20 minutes until light brown. When the cookie bottom is done, take it out of the oven and let cool for about 5 minutes before adding the top.
Meanwhile mix all the ingredients for the lemon top in a saucepan and heat over medium heat, stirring constantly, until the mix coats the back of a spoon. Yes, Martha, this is a custard.
Mix the cream cheese, salt and lemon zest together until smooth. OK, I confess, I use my food processor, but you can do this by hand. Mix in the condensed milk (whisk by hand, pulse by machine) until smooth. Mix in the egg. Mix in the lemon juice. Your mixture will thicken somewhat. Yes, Martha, this is like classic key lime pie...sort of.
Meanwhile back to the main recipe using whichever top you've picked. Isn't cooking fun?
Evenly spread the lemon mix on top of the cookie bottom.
Put it back into the oven for 15-20 minutes, turning the baking pan about half way through the time. Take out of the oven and cool for at least 2 hours. Really. It won't cut right if you try to rush this.
After it has cooled completely, use the lining paper or foil to pull the whole thing out of the pan. I trim off the edges which are usually uneven (that's for the cook to eat) and then cut up the bars into squares, or rectangles, or whatever you like. Dust with powdered sugar.