Beef bone marrow in Instant Pot or pressure cooker comes out so tender you can spread it on toast. It's also a great way to make homemade beef stock at home too.
Put sliced onion on the bottom of the pot with beef bone marrow pieces on top of those. Drop minced garlic around pieces with a sprinkle of salt and pepper on top of everything. (if you want to make stock as well I would add large chunks of celery and carrots + a sprig of thyme and parsley).
Pour enough water into the pot just so pieces are submerged, in a 6 qt. pressure cooker 8 cups was enough.
Close the lid and steam valve. Cook on high pressure for 25 minutes.
Allow for a natural release which will take about 20 minutes. Lift lid and enjoy marrow.
Lift bones out and use a spoon to release or remove the marrow in the middle. Some may have released so you can use a slotted spoon to scoop those out. Add into a small bowl to use as a spread or otherwise.
If you want to make and save stock that is left, put a strainer inside a pot to drain the liquid. Pour liquid from pot into jars. If storing in jars make sure they cool completely first, before transferring them into the fridge.
After a few hours the fat will rise to the top, skim that off and then use as you wish up to 4 days after that.