Put all ingredients into the Instant Pot, except the tomatoes and stir well.
Pour the tomatoes on top and do not mix. This is to prevent any chance of them burning and sticking to the bottom.
Cook on High Pressure for 10 minutes, allowing it to release pressure naturally.
Using an immersion blender, purée the sauce carefully. You may have to tilt your liner to blend all of it. If you don't have an immersion blender, wait for the sauce to cool a little, and use your blender. Be sure to remove the little inside piece on the blender lid to allow steam to escape.
Use half the sauce right away and freeze the rest. You'll probably need about 1 cup of this sauce for 6-8 enchiladas.
This sauce is freezer-friendly! Make one batch and freeze the rest.
This stores in the fridge for up to a week.
If you can't find fire-roasted tomatoes, you can use regular canned tomatoes.