Preheat oven to 350°F. Over medium heat, add olive oil to a pan on the stovetop and cook the diced jalapeños and onions with salt until softened and glossy, about 6 minutes.
Add the minced garlic and sauté until fragrant, about 1-2 minutes.
Process canned black beans (one can rinsed and strained, the other can with the liquid included) in a food processor with the cooked onions and jalapeños, lime juice, and apple cider vinegar until smooth.
Pour the black bean dip into a 9” cast iron skillet or another oven-safe dish and sprinkle shredded cheddar cheese and chili powder on top.
Place the skillet into the preheated oven and bake until the cheese is fully melted.
Serve hot with your favorite tortilla chips and toppings, if desired.