Position a rack in the top third of the oven and preheat to 425 degrees F. Line a rimmed baking sheet with parchment paper.
Toss the panko, Parmesan, parsley, 1/2 teaspoon salt and 1/4 teaspoon black pepper together in a small bowl. Arrange the tomatoes in the center of the prepared baking sheet, cut-side up (trim a small slice from the bottom of each tomato if they will not stand upright) and spoon the panko mixture evenly over each. Spray the breadcrumbs lightly with cooking spray. Lay the zucchini halves cut-side up on one side of the tomatoes. Drizzle zucchini with 1 tablespoon of the olive oil and sprinkle with salt and pepper. Roast until the vegetables begin to soften and the panko topping begins to brown, about 18 minutes.
Remove the baking sheet from the oven and place the salmon fillet on the other side of the tomatoes. Drizzle the salmon with the remaining 1 tablespoon olive oil and sprinkle with salt and pepper. Roast until the zucchini and tomatoes are completely tender and browned in spots, and the salmon is cooked through but moist, about 12 minutes more. Divide salmon and vegetables between two plates and serve.
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