My mother used to make this all the time when I was a kid. I had the recipe for several years, until it was lost during one of the many times I moved. I got it back by visualizing my mother making it. Thank goodness for "mind movies".
Take the lemon, grate off the skin (forming lemon zest); cut lemon in half and squeeze out all the juice. Set aside.
Cream butter and cream cheese together, then add beaten egg and mix in. Next, mix in the sugar and the milk. Pour in the lemon juice, mix, and mix in flour. Finally, mix in the lemon zest. Pour into the graham cracker crust.
Bake in a 325 degree oven for 30-35 minutes, checking to make sure that the cheesecake doesn't bake too long and dry out. I used to sneak slices of this in the middle of the night when I was a kid.
You can make this a lower-fat recipe by using low-or no-fat cream cheese, skim milk, and a reduced-fat graham cracker crust. It still tastes like a guilty pleasure.