Thaw fish, if frozen. Rinse salmon and pat dry with paper towels. Preheat oven to 400°F.
Lightly coat a 3-quart baking dish with nonstick cooking spray. In the baking dish, combine tomatoes, shallots, garlic, oregano, olive oil, ¼ teaspoon of the salt, and ¼ teaspoon of the pepper. Toss to coat.
Roast, uncovered, for 15 minutes. Place salmon, skin side down, on top of the tomato-shallot mixture. Sprinkle salmon with the remaining ¼ teaspoon salt and the remaining ¼ teaspoon pepper. Roast, uncovered, for 15 to 18 minutes or until salmon flakes easily when tested with a fork. Use two large pancake turners to transfer the salmon to a cutting board.
Reserve two-thirds of the cooked salmon for another meal (see Tip).
If desired, use the turners to lift the salmon meat off the skin and onto a large platter; discard skin. Serve the remaining salmon with the tomato-shallot mixture.
Tip: Divide the reserved cooked salmon between two airtight containers. Cover and store in the refrigerator for up to 3 days or freeze up to 3 months.