Grilled Peach, Onion, and Bacon Salad

Salad:

• 1/2 lbs thick-sliced bacon
• 2 tbsp brown sugar
• 1/4 tsp cayenne pepper
• 1.5 lbs Vidalia or other sweet onions, cut into 1" thick slabs (about 2 large)
• 2 tsp olive oil
• 4 medium ripe, but still firm, yellow peaches, cut into 1/2" wedges

Dressing:

• 1/2 cup buttermilk
• 1/2 cup sour cream
• 1/4 cup finely chopped mixed fresh tender herbs (such as tarragon, chive, parsley, and/or dill)
• 2 tbsp fresh lemon juice
• 1 small garlic clove, finely grated (using a micro plan or minced)
• 1 pinch kosher salt
• 1 pinch ground black pepper