Preheat the oven to 450°F (230°C).
Line a baking sheet with aluminum foil and lightly coat the foil with cooking spray.
Pat the salmon fillets dry with paper towels, then brush both sides with 3 to 4 tablespoons olive oil.
Sprinkle Greek seasoning evenly over the top of each fillet, pressing gently so it adheres.
Place the fillets skin-side down (if applicable) on the prepared baking sheet, spacing them slightly apart.
Bake on the middle rack for 13–15 minutes, or until the salmon is opaque and flakes easily with a fork.
Remove from the oven and let rest for a couple of minutes before serving with tzatziki sauce.