Add in the pinto beans, stock, chili powder, cumin and oregano. Stir to combine. Continue cooking until the mixture reaches a simmer.
Reduce the heat to low and remove the lid. Use a potato masher or the back of a fork to mash up about at least half of the beans to your desired consistency. Continue to cook the beans, uncovered, stirring often, for 3 more minutes.
Stir in remaining tablespoon of butter until melted and well combined. Season with cilantro, citrus juice, salt and pepper to taste.