In a medium saucepan, add olive oil and bring to medium heat. Add red onion, green bell pepper, red pepper and mild green chiles. Sauté for 2-3 minutes. Stir once or twice.
Add garlic and cook for 30 seconds to 1 minute until fragrant. Stir to combine.
Add black beans with juice, chili powder, cumin and salt. Stir to combine. Bring to a gentle boil.
Reduce heat to medium low, maintaining an aggressive simmer. Cook black beans uncovered for 30-40 minutes, stirring often.
Off heat, with a potato masher or an immersion blender lightly mash 1/2 of the black bean mixture. Leave additional beans whole. Stir to combine.