Preheat oven to 400 degrees F. Arrange bell pepper halves cut-side up on a large rimmed baking sheet. Brush with olive oil and sprinkle with salt. Roast for 12 to 15 minutes until just tender but still holding their shape. They will not be fully cooked yet.

While peppers roast, heat a large skillet over medium-high heat. Add ground beef and cook, breaking it up with a wooden spoon, until no pink remains, about 6 to 8 minutes. Drain excess fat if needed. Stir in taco seasoning and water, then simmer for 2 to 3 minutes until the mixture thickens slightly and looks saucy but not wet.

Remove peppers from oven. Divide the seasoned beef evenly among the pepper halves, pressing it down slightly. Top with shredded cheese, then scatter black beans and pickled jalapenos over the cheese. Return to the oven and bake for 10 to 12 minutes until the cheese is fully melted and bubbling with light golden spots.

Let the nachos rest for 3 minutes so the cheese sets slightly. Transfer to a serving platter or serve directly from the baking sheet. Top with dollops of sour cream, a sprinkle of fresh cilantro, and serve salsa on the side for drizzling or dipping.