Preheat your oven to 425°F (220°C).
Peel and dice the sweet potato into 1-inch cubes. Toss the cubes with half of the olive oil and a pinch of salt and pepper. Spread them evenly on a baking sheet.
Roast the sweet potato in the oven for about 20-25 minutes, or until tender and slightly caramelized, stirring halfway through.
Meanwhile, trim the ends of the green beans. Toss them with a small drizzle of olive oil, salt, and pepper, and set aside.
Heat a non-stick skillet over medium-high heat. Add the green beans and sauté for 5-7 minutes until they are bright green and tender-crisp. Remove and keep warm.
Season the 5-ounce tuna steak lightly with salt and pepper. Increase the heat of the same skillet and add a teaspoon of olive oil. Once hot, sear the tuna for about 1.5 to 2 minutes per side, depending on thickness, until the exterior is beautifully crisp while the center remains slightly rare.
Plate the seared tuna, and serve with a generous portion of roasted sweet potatoes and sautéed green beans. Enjoy your balanced, nutritious meal with a perfect blend of protein, healthy fats, and vibrant vegetables.