Place beans and salt in a large pot. Add in enough water to cover the beans by at least 3 inches.
Cook over high heat until the water starts to boil, then reduce heat to low and simmer for 2-3 hours or until the beans are tender. Be sure to check on the beans often while they are cooking and add more water as needed to keep them covered.
When beans are tender, drain most of the water from the pot. Add the onion powder to the beans.
Using an immersion blender, blend beans until smooth. If you do not have an immersion blender a potato masher may also be used. As you are blending the beans add in more warm water as needed until the desired consistency is reached.
Taste beans, and add more salt or onion powder if needed. You can also stir in other spices if you would like. See the variations listed below for some ideas!
Serve warm as desired. Enjoy!
Notes
These beans are a "blank slate" and it is easy to add more to them. Here are some additions you can stir in after they are done blending:
Fresh garlic or garlic powder
Chopped cilantro
Chili powder
Cumin
Lime juice
Cheese
You can also try using different types of beans, and black beans are especially delicious. Have fun trying new flavor combinations!