Add the bacon to a large pot or dutch oven over medium heat and cook for 10 minutes, until the fat has rendered and the bacon is crispy. Transfer it to a bowl and set aside.
Season the beef with 1 teaspoon kosher salt. Add the meat to the same pot and cook for 10 minutes until browned.
While the meat is browning, make the tomatillo sauce. Add the tomatillos, serrano peppers, ½ cup of the chopped cilantro, garlic, cumin, black pepper, water, and the remaining 2 teaspoons of kosher salt to a large blender. Blend until smooth.
When the meat has browned, pour in the tomatillo sauce. Stir to combine, bring to a boil, then reduce heat to simmer. Cover and cook for 30-35 minutes, until meat is tender.
Stir in the pinto beans and cook for 2 more minutes until warmed through.
Serve in bowls garnished with crispy bacon, diced onions, chopped cilantro, thinly sliced radishes, and a squeeze of fresh lime juice.
Notes
Bacon: The bacon and bacon fat add a delicious depth of flavor to this dish, but you can use 3-4 tablespoons of olive oil instead if you prefer.