Preheat an outdoor grill to 375 degrees F (190 degrees C) and lightly oil the grate.

Arrange potatoes on the grill grate and grill, flipping occasionally, until just barely tender when poked with a skewer, about 15 minutes. Let them cool until they are easy to handle.

Cook the bacon in a skillet over medium heat until the grease becomes foamy, approximately 5 minutes. Remove half of the bacon with a slotted spoon, drain on paper towels, and set aside for topping. Add the diced onion to the remaining bacon in the skillet and cook until translucent, about 5 minutes more.

While the bacon and onion are cooking, peel the grilled potatoes, cut them into quarters, and then into 1/2-inch slices. Place them in a bowl.

Stir in the white wine vinegar, sugar, salt, black pepper, and cayenne pepper into the bacon-onion mixture. Increase the heat to medium-high and bring the dressing to a boil. Stir well and remove from heat.

Pour the warm dressing over the potatoes and toss to combine. Let it sit for 5 minutes, then stir again. Add the chopped parsley and top with the reserved bacon. Enjoy this salad warm.

Chef's Note: Adjust the amount of bacon used based on your preference. If using less bacon, compensate with vegetable or olive oil in the dressing. For a tangier dressing, add more vinegar, or adjust with vegetable oil for a milder flavor.