On sauté setting, brown the ground beef with the garlic and onion.
While the meat is browning, combine the ricotta cheese with the Parmesan and egg in a small mixing bowl.
Drain grease and remove browned beef to a 1 1/2 quart soufflé dish (or similar dish that fits into Instant Pot). Add the marinara sauce to the browned meat and reserve half of the meat sauce. (See Recipe Notes on how to make the lasagna directly in the pot without burning... basically, you'll want to add more sauce so there's plenty of liquid cooking under pressure)
(Note, the water and rack is not needed if adding more sauce and cooking directly in the pot) Pour 1 cup water into pot then place soufflé dish on rack over water. You may want to use a sling to easily remove the soufflé dish when done. Cover, and cook at high pressure for 8-10 minutes.
Since so many comments noted that the lasagna burned in their pot, the recipe has changed to use the pot in pot (PIP) method rather than cook directly in the pot.
However, the issue with burning is if there isn’t enough liquid in the pot when cooking under pressure. So a “watery” sauce is what’s needed to keep the lasagna from burning if you don't want to use the PIP method. Extra sauce should also prevent burning for those wanting to cook directly into the pot.