Heat oil in a skillet over medium-high heat. Add onion and sauté 3 minutes, or until light and translucent. Add garlic and cook, stirring often, for 2 minutes. Remove from heat.
Combine sautéed onion and garlic, beans, diced tomatoes, ½ cup cilantro, cumin, chili powder, salt and pepper in a slow cooker. Stir until combined. Cover and cook on low 2 hours.
Serve warm, topped with more cilantro, shredded cheese, and Mexican crema or sour cream.
