Heat oven to 450 degrees. Line a rimmed baking sheet with parchment paper.

Put the carrots on the prepared baking sheet. Drizzle with 2 tablespoons of olive oil, season with ¾ teaspoon of salt and plenty of pepper and toss to coat. Spread out in a single layer. Roast, tossing halfway through, for 20 minutes.

Meanwhile, finely grate the zest of the lemon into a small bowl. Cut the lemon in half crosswise and reserve for serving. Finely grate the garlic into the bowl. Add the cumin seeds and stir to combine.

Pat the salmon dry, rub with the remaining 1 tablespoon of olive oil and season both sides with the remaining ¾ teaspoon of salt and several grinds of pepper. Sprinkle the top of each fillet with the cumin seed mixture and press lightly to adhere.

Remove the baking sheet from the oven and reduce the oven temperature to 400 degrees. Toss the carrots then push them aside to make 4 spaces for the salmon fillets. Place the fillets in the empty spaces.

Return to the oven and roast until the salmon is just cooked through, about 10 minutes. It’s done when the flesh is just able to flake easily. An instant-read thermometer inserted into the middle of the thickest part should register 120 degrees for medium-rare. If you prefer medium, cook it a few minutes longer.

Squeeze the reserved lemon over the top of the salmon and carrots before serving and garnish with parsley, if using.