In a medium bowl, whisk together the vegan mayonnaise, prepared mustard, white wine vinegar, black salt, and freshly ground black pepper until you have a smooth, creamy dressing.
Add the finely diced celery, dill pickle, and minced onion to the dressing and stir to combine.
Gently fold in the diced extra-firm tofu, mixing until all the pieces are evenly coated.
For best results, cover and refrigerate for at least 15 minutes to allow the flavors to meld together before serving.
Add a pinch of turmeric to the dressing to give your 'egg' salad a realistic yellow color. A tablespoon of fresh chopped dill or chives also adds a wonderful burst of freshness.