How many servings does this recipe make?

This recipe makes 4 servings. You can adjust the portion size directly on this page.

What ingredients do I need for Seared Tuna Sandwich With Balsamic Onions?

You need 14 ingredients. The key ingredients include: 2 teaspoons butter, 2 cups vertically sliced onion, 1 1/2 tablespoons balsamic vinegar, 1/4 teaspoon dried thyme, and more.

Is Seared Tuna Sandwich With Balsamic Onions suitable as seafood?

Yes, Seared Tuna Sandwich With Balsamic Onions falls under the Seafood category and is a great choice for this type of meal.

How do I store leftover Seared Tuna Sandwich With Balsamic Onions?

Store leftovers in an airtight container in the refrigerator for up to 3–4 days. Reheat gently before serving.

Seared Tuna Sandwich With Balsamic Onions Recipe

Name: Seared Tuna Sandwich With Balsamic Onions
Prep time: 15 min
Cook time: 30 min
Total time: 45 min
Yield: 4 servings
Ingredients: 2 teaspoons butter; 2 cups vertically sliced onion; 1 1/2 tablespoons balsamic vinegar; 1/4 teaspoon dried thyme; 1 tablespoon all-purpose flour; 1/2 teaspoon salt; 1/4 teaspoon garlic powder; 1/4 teaspoon black pepper; 4 (6-ounce) tuna steaks (about1/2 inch thick); Cooking spray; 4 teaspoons Dijon mustard; 4 (2-ounce) whole wheat hamburger buns; 4 curly leaf lettuce leaves; 4 (1/4-inch-thick) slices tomato

Try this homemade Seared Tuna Sandwich With Balsamic Onions recipe the whole family will love. Made with butter, onion, balsamic vinegar and thyme. Easy…

This Seared Tuna Sandwich With Balsamic Onions relies on simple, everyday ingredients such as butter, vertically sliced onion, balsamic vinegar and dried thyme. It comes together quickly and makes 4 servings, at about 552 kcal each. The step-by-step instructions below are written to be easy to follow, even on a busy day.

It's versatile enough for an easy weeknight dinner yet satisfying enough for guests at the weekend. Serve it with your favorite sides, and keep any leftovers for a quick meal the next day.

Updated Jun 30, 2026

Serves 4 Seafood

Tips for the best results

Read through all the steps once before you start and measure out your ingredients first — it makes everything go more smoothly.
Taste as you go and adjust the seasoning before serving.
Avoid overcrowding the pan — cook in batches if needed for the best texture.
Let the dish rest for a few minutes before serving so the flavors settle.
Store leftovers in an airtight container in the fridge and enjoy within a few days.

Variations & substitutions

Use a neutral oil or a plant-based spread in place of butter for a dairy-free version.
A good 1:1 gluten-free flour blend works well if you need a gluten-free version.

No specific allergen information. Please check the ingredient list for possible allergens.

My Personal Notes

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Seared Tuna Sandwich With Balsamic Onions

Tips for the best results

Variations & substitutions

My Personal Notes

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