Into the Ninja Creami pint container, add all of the ingredients except the lemon zest. Stop a tad short of the max fill line (lemon juice causes a little bit more expansion in the freezer). Use an immersion blender to blend until smooth.
Place lid on the pint container. Freeze for 24 hours on a flat, level surface.
When ready to eat, install the pint container into your Ninja Creami as specified per the instructions for your model.
Spin once on "Lite Ice Cream." Check the texture after the spin to see if it's ready.
If needed, put the ice cream container back in the machine and press "re-spin."
Video
Notes
⭐Using 50 grams of protein powder replaces the heavy cream in typical ice cream and makes this low-fat ice cream thick and smooth. I don't recommend using less unless you're okay with thinner ice cream.⭐If you do not eat the whole pint at once, flatten the top with the back of your spoon before putting it back in the freezer. When you want to eat the rest, spin it in your machine using the "Lite Ice Cream" setting. Do a re-spin afterwards if necessary.