Preheat oven to 400°. Salt and pepper salmon fillets and place on a parchment covered sheet pan. Bake 15-20 minutes, or until fully cooked (depending on thickness of fillets and desired doneness).
While salmon bakes, melt butter in a sauté pan on medium high heat and cook onions until they begin to soften. Add a pinch of salt. Add half of the grapes, olives, and cook until grapes start to release their juice. Remove from the heat and add parsley and green onion. Add remaining grapes, vinegar and zest. Add lemon juice to taste.
Top salmon with grapes and enjoy!