Cook the ground beef: Heat a skillet over medium heat. Add the ground beef, breaking it apart with a spoon. Cook until fully browned, about 7-10 minutes. Season with salt and pepper, then remove from heat and set aside to cool slightly.

Prepare the vegetables: While the beef is cooking, wash and chop the romaine lettuce into bite-sized pieces. Halve the cherry tomatoes, thinly slice the red onion, and dice the dill pickle.

Assemble the salad: In a large salad bowl, combine the chopped romaine lettuce, cherry tomatoes, red onion slices, shredded cheddar cheese, and diced dill pickle. Toss to mix well.

Add the beef: Once the ground beef has cooled slightly, add it to the salad mixture. Toss again to distribute the beef evenly throughout the salad.

Make the dressing: In a small bowl, whisk together the olive oil, Dijon mustard, and mayonnaise until smooth. Adjust seasoning with salt and pepper if needed.

Dress the salad: Pour the dressing over the salad and toss to coat all ingredients evenly.

Serve: Divide the salad into individual bowls. Top each serving with avocado slices. Enjoy immediately.