In a removeable insert of a 6-quart slow cooker (or a large 10-inch skillet if your slow cooker does not have a stove-top safe insert) set over medium heat, cook the bacon several minutes, stirring regularly, until bacon starts to brown and renders its fat. Add the onion and cook until golden, about 6-8 minutes. Add garlic and jalapeños and cook until the garlic begins to brown and is fragrant, about 1 minute. Stir in the tomatoes and cook another minute.
Fit the insert into the slow cooker (or transfer the mixture from the skillet to the slow cooker) and add the beans, 1 teaspoon of salt, and 7 cups of water. Cover and turn the slow cooker to high. Your beans will be done in 3 to 4 hours, though you can hold them for longer. (My slow cooker can be programmed to switch from high after 3 ½ hours to a “keep warm” temperature for another 6 hours. Some slow cookers click to “keep warm” automatically; others need to be switched manually.)
When ready to serve, remove 2 cups of the beans and process in a blender or food processor until smooth. Add the smooth beans back to pot and stir in the cilantro. Taste and season with more salt if needed. Ladle into bowls and serve.
No Slow Cooker?
Follow the directions for cooking the bacon, onion, garlic, chiles and tomatoes in a medium-large (4- to 6-quart) pot (preferably a Dutch oven) over medium-high. Add the beans, salt, and 2 ½ quarts water. Bring to a rolling boil, then reduce to medium-low and cook the beans at a gentle simmer, partially covered, until thoroughly tender, about 2 hours. (You’ll find it necessary to add water from time to time to ensure that the level of liquid remains about the same.) Finish the recipe as directed above.