In a medium bowl, combine the tomatoes, 4 tablespoons olive oil, olives, thyme, capers, and garlic. Let stand in the refrigerator for at least 30 minutes and up to 2 hours.
Turn on the oven grill (medium to high heat) or prepare the barbecue.
Season the salmon with salt and pepper to taste.
In a medium bowl, whisk a little bit of oil with mustard, ground pepper, and a bit of minced garlic.
Spread the fresh thyme in an ovenproof pan. Place salmon fillets or steaks over it. Brush the salmon fillets with the mustard sauce and then grill.
Serve with the tomato, olives, thyme, capers, and garlic.