For the jalapeno(s), washed and pat them dried. Prepare a large heatproof bowl and cover with a plastic wrap. Turn the heat to medium on the gas stove, place 1 jalapeno on the metal grate on the open flame. Let it roast until the skin is charred and blackened on all sides, rotating with a metal tongs or long metal skewer. Place the roasted jalapeno in the prepare bowl and cover the bowl securely with the plastic wrap. Set aside for 15 minutes. It will create steam inside the bowl and make it easy to remove the charred skin. If using 2 jalapenos, repeat the steps with the 2nd one.
In a large skillet over medium heat, warm the oil. Add onion and bell pepper. Sauté until soften and golden brown, about 15 minutes, stirring occasionally. Try not to brown too much. If needed, add a teaspoon of water to prevent browning. Stir in the garlic and cook for 1 more minute.
Place the jalapeno(s) on a chopping board, rub the charred skins off the jalapeno with your fingers. Remove the stem with a knife and cut the jalapeno(s) in half lengthwise. Remove the seeds and roughly chop the jalapeno(s). Place in a small bowl.
In a blender or food processor, add ½ cup water, the onion mixture, black beans ( with the liquid), Monterey Jack cheese, ½ ounce cotija cheese, and 1 jalapeno. Blend until pretty smooth. If needed, add a little bit more water, so the machine can blend easier. Taste and check to see if it’s spicy and cheesy enough. Add more jalapeno and cotija cheese if needed. If it’s salty enough, do not add more cotija cheese. Blend until smooth, about 2 - 3 minutes.
In a medium pot, pour in the bean dip. Bring to a simmer over medium-high heat. Once simmering, turn the heat down to medium-low and cook until slightly thickened, about 25 minutes, stirring occasionally. Season with salt if needed. The dip will thicken more as it cools.
Transfer the dip to a serving bowl. Stir in the crema or sour cream if using. Crumble some cotija cheese and sprinkle on top. Zest the lime over the dip and tortilla chips. Serve warm.