Add cream cheese to a large mixing bowl. Use the paddle attachment to beat until light and creamy, about 1 minute. Scrape down the sides of your mixing bowl a few times as needed to make sure all the cream cheese gets beaten.

Add in the condensed milk. Beat until the condensed milk is fully incorporated and the mixture is very smooth. You want to make sure there are no lumps of cream cheese. Add in the lemon juice. Fold it in until it is evenly incorporated. You should see the mixture thicken almost instantly. Taste, and you can adjust filling as needed. You can add a little more condensed milk, a little more lemon juice or a little more cream cheese as needed. Let filling rest for about 5 minutes to thicken more.

Transfer cheesecake filling into the graham cracker pie crust. Use an offset spatula to smooth the surface. Place cheesecake into the fridge for 3-4 hours, or overnight, to set. If you want to decorate the cheesecake, wait for the filling to set and then decorate. Keep the cheesecake in the fridge until ready to serve. Optional step: 60 minutes before you plan on cutting the cheesecake, place it into the freezer. This will firm up the crust, making it much easier to cut clean slices without the crust falling apart. The cheesecake filling will be a little firm straight out of the freezer but will soften after a few minutes at room temperature. Store any uneaten cheesecake in an airtight container in the fridge or freezer.