Let's cook.
Preheat your oven to 400°F (200°C). Line a large baking sheet with parchment paper.
In a small bowl, combine the olive oil, dried oregano, garlic powder, salt, and black pepper. Whisk well.
Place the salmon fillets and chopped vegetables (cherry tomatoes, zucchini, and red onion) on the prepared baking sheet. Drizzle the olive oil mixture evenly over the salmon and vegetables, tossing the vegetables to coat.
Arrange the lemon slices over the salmon fillets and scatter any remaining slices among the vegetables.
Roast for 15-20 minutes, or until the salmon is cooked through and flakes easily with a fork, and the vegetables are tender-crisp. The internal temperature of the salmon should reach 145°F (63°C).
Remove from the oven and squeeze the juice from the remaining lemon half over the entire dish before serving.
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