Method
Oven
Preheat oven to 325° F.
Heat oil in a large pot over medium high heat. Add onions and cook for 5 minutes until softened and beginning to caramelize.
Add remaining ingredients and simmer for 5 minutes.
Transfer beans to a casserole dish and bake for 50 minutes until thickened.
Slow Cooker
Add all of the ingredients listed above into slow cooker.
Add 1/2 cup water, and cook on high for 4 hours until thickened.
Instant Pot
Set the instant pot to saute function.
When hot, add oil and onions, and cook for 5 minutes until softened and beginning to caramelize. Turn off instant pot.
Add remaining ingredients and close lid. Be sure to set the vent to "sealing" mode.
Cook at high pressure for 15 minutes. When done, use immediate release to relieve pressure, remove lid and stir.