Preheat your oven to 350 degrees F.
In a medium bowl, combine the cream cheese and mayonnaise. Mix until completely smooth and well incorporated.
Add in the small diced sweet onion and freshly grated Parmesan cheese to the mixture. Stir gently to combine.
Sprinkle in the freshly ground black pepper and mix again until everything is fully blended.
Transfer the dip to a small baking dish, spreading it evenly across the bottom.
Place the dish in the preheated oven and bake for about 45 to 55 minutes.
Once it’s out of the oven, let the dip cool for a few minutes before serving.
Serve the Sweet Onion Parmesan Dip hot, alongside your choice of baguette slices, crackers, or chips.