I generally use a combo of Rainbow peppercorns freshly ground, with garlic powder and onion powder moderately sprinkled on top.
However, my all time favourite topping is to make a homemade BBQ sauce that is salt and sugar free.
I take an onion, and finely chop it. I then saute it over medium heat for about an hour, caramelizing it but not burning it. Then I add a can of chopped tomatoes, a tablespoon of tomato paste, three tablespoons of apple cider vinegar, and three tablespoons of Worcestershire sauce.
Let it all meld while simmering. If you want it nice and smooth, just puree it in a Cuisinart and then strain it through a mesh strainer. Or just spoon lumps and all on the chicken, and bake. So tasty, and healthy!
Or you can use this recipe I have for homemade salsa verde.
Homemade salsa verde: [oven roasted green onions (1 bunch), 8 med size tomatillos (peeled),2 jalape?os (cut and deseeded), 6 garlic cloves]. Blend with 1/2 squeezed lime juice, handful of cilantro. Add chipotle powder or roast more jalape?os to make spicier.