Sauté the onions in the bacon fat until softened, about 2-3 minutes, using the Instant Pot sauté function.
Add the remaining ingredients (except tomatoes and salt) and stir to combine.
Pressure cook on high for 50 minutes.
Let the pressure release naturally for 15 minutes, then use the quick release for any remaining pressure.
Stir in the tomatoes and add the salt, if necessary. (Taste before adding salt).
Remove any ham from the bone, chop up and put back in the soup.
Notes
For the best flavor, I highly recommend using bacon fat, but butter or oil will also work.
Similarly, I suggest toasting your cumin seeds for maximum flavor.
Taste the soup first before adding any salt. The ham or pork hock will be salty, so you may only need to add a little salt to suit your taste.
Be sure to let the pressure naturally release for 15 minutes as the beans will continue to cook during this time. If you do a quick release, the beans may still be a little firm.
After all of the pressure releases, be sure to remove the soup from the Instant Pot. If you let it keep warming, the beans may start to get mushy.
While the cook time is 50 minutes in the Instant Pot, you’ll also need to factor in time for pressure to build and release.