A complete sheet pan dinner that feeds 4 people in just 40 minutes? It doesn't get much better than this fuss-free dinner prep method. You'll only need a few pantry-staple ingredients in addition to the fish, veggies, and potatoes. The Tzaziki sauce is optional, but we highly suggest serving it with the final dish for over-the-top flavor (Plus--you'll have time to prepare it while the potatoes are cooking).
Add potatoes to a large, 12x17-inch rimmed baking sheet lined with aluminum foil. Drizzle with 1 tablespoon olive oil and sprinkle with ¼ tsp. each salt and pepper; toss to coat. Arrange potatoes cut-side down and roast until potatoes are fork-tender, 20-25 minutes.
While potatoes are cooking, prepare Tzatziki Sauce and place in the refrigerator to chill.
A few minutes before the potatoes are done cooking, trim green beans and place in a large bowl. Drizzle with remaining 1 tablespoon olive oil and sprinkle with ¼ tsp. each salt and pepper; toss to coat.
Remove potatoes from the oven and preheat broiler.
Season salmon with remaining ¼ tsp. each salt and pepper. Carefully place salmon in center of baking sheet and arrange potatoes and green beans in a single layer around salmon. (Move potatoes to edges of pan with a spatula so that salmon can be placed in center of the pan.)
Squeeze lemon halves over entire sheet. Slice lemon halves and add to baking sheet, if desired.
Broil salmon, green beans, potatoes, and lemons 10 minutes, or until salmon is no longer translucent but still moist in center and green beans, potatoes, and lemons are lightly browned. Serve with Tzatziki Sauce.