Preheat your oven to 425°F (220°C).
Rinse and pat dry the salmon fillet and tuna steak. Season both sides lightly with salt and pepper.
For the potatoes, rinse them thoroughly, then halve if necessary for even cooking. Toss them in a bowl with half of the olive oil, salt, and pepper.
Spread the potatoes on a baking sheet and roast in the preheated oven for about 20-25 minutes until they are golden and crispy.
While the potatoes are roasting, heat a non-stick skillet over medium-high heat. Add a small drizzle of olive oil.
Sear the tuna steak in the skillet for about 1-2 minutes per side to achieve a slightly rare center, then remove from the heat.
Using the same skillet, add the salmon fillet and sear it for about 2-3 minutes per side. If the salmon needs a bit more cooking, finish it in the oven for an additional 5 minutes.
For the green beans, blanch them in boiling water for 2-3 minutes until they turn bright green and remain tender-crisp, then quickly transfer to ice water to stop the cooking.
Plate the roasted potatoes, arrange the green beans alongside, and place the seared salmon and tuna on top. Drizzle any remaining olive oil over the fish if desired.
Serve immediately and enjoy this balanced and flavorful meal.