Preheat and prep: Heat your oven to 425°F (220°C). Line a large sheet pan with parchment paper or lightly oil it.
Season the veggies: In a large bowl, toss the broccoli, bell pepper, red onion, zucchini, and cherry tomatoes with 2 tablespoons olive oil, half the lemon zest, half the garlic, oregano, thyme, smoked paprika, salt, and pepper. Spread them in an even layer on the sheet pan.
Start roasting: Roast the veggies for 10 minutes to give them a head start so they caramelize nicely.
Prepare the salmon: While the veggies roast, pat the salmon dry with paper towels.
Rub with the remaining 1 tablespoon olive oil, the rest of the lemon zest and garlic, a pinch of salt and pepper, and red pepper flakes if using.
Add the salmon to the pan: Remove the sheet pan from the oven. Push the veggies to the edges to make space and place the salmon fillets skin-side down in the center.
Roast to perfection: Return the pan to the oven and bake for 10–12 minutes, or until the salmon flakes easily with a fork and reaches an internal temperature of 125–130°F for medium (or 135°F for more well-done).
Finish with lemon: Squeeze the lemon juice over the salmon and veggies right after baking. The fresh acidity brightens the flavors.
Garnish and serve: Sprinkle with chopped parsley or dill.
Serve with extra lemon wedges and your favorite grain, like quinoa, couscous, or rice, if you want more substance.