Whip the heavy whipping cream cold from the fridge until soft peaks form and the mixture thickly coats the back of a spoon.
Turn the mixer on high speed and continue to whip, adding the sweetened condensed milk in a steady stream until it's fully incorporated and the mixture almost reaches the hard-peak stage.
Continue whipping as you add the lemon juice and zest just until it's incorporated. You'll notice the mixture thickens after adding the lemon - this is good!
Be careful NOT to over-whip, as this will cause the fat and the water in the cream to separate. If this happens, the ice cream will NOT freeze properly and won't have the creamy, smooth texture you desire.
Line a large loaf pan with parchment paper (or use a resealable plastic freezer-safe container, if you prefer) and scrape the cream mixture into the pan or container.
Cover with plastic wrap (or a lid) and freeze for about 6-8 hours, or until the ice cream has become solid enough to scoop.
Serve with some lemon zest and fruit, or however you desire.