Heat a charcoal or gas grill to medium-low, about 300°F.

Brush ribs with olive oil and grill for 45 minutes per side or until tender.

Melt butter in a pot, add onion and cook for 10 minutes or until soft.

Add mustard, relish, brown sugar, apple cider vinegar and celery salt and simmer over medium heat while stirring occasionally for 15 minutes.

Once your ribs are tender brush them with half the sauce and continue grilling until the sauce is cooked on.

Remove ribs from the grill, let stand for 10 minutes, brush them with the remaining sauce and sprinkle the diced sport peppers onto them.