Prepare the Dressing: In a medium-sized bowl, whisk together the vegetable oil, white vinegar, granulated sugar, mustard powder, garlic powder, salt, black pepper, and cayenne pepper (if using). Set the dressing aside.

Combine the Vegetables: In a large mixing bowl, add the chopped cauliflower, broccoli, carrots, celery, bell pepper, red onion, drained mushrooms, and drained baby corn.

Marinate the Salad: Pour the prepared dressing over the vegetables. Mix everything thoroughly to make sure the vegetables are fully coated with the dressing.

Refrigerate Overnight: Cover the bowl and refrigerate the salad overnight, or for at least 8 hours, to allow the flavors to meld and the vegetables to absorb the dressing.

Serve: Before serving, toss the salad again to redistribute the dressing. Serve chilled and enjoy the zesty flavors!