Preheat the oven to 425˚F and line a rimmed baking sheet with foil.

In a large skillet, add olive oil and set over medium heat. Add ground beef and cook, breaking up the beef with a fork, for 5 to 7 minutes, or until only some pink remains. Add chili powder, cumin, salt and pepper and cook for 1 to 2 minutes more, or until cooked through. Remove from heat.

Scatter tortilla chips in a single layer on the prepared baking sheet. Top with beef, black beans and cheddar cheese. Place in the oven and bake for 5 to 7 minutes, or until the cheese is melted.

Let cool slightly, then distribute the salsa and sour cream evenly on top of the nachos. Scatter scallions and jalapeño slices (if using), and avocado on top. Serve with fresh lime wedges on the side, and squeeze lime juice on top right before enjoying.