Preheat your oven to 375°F (190°C).

In a large skillet, heat olive oil over medium heat. Add diced white onion and chopped Bella mushrooms, sautéing until translucent and mushrooms release moisture, about 5–7 minutes.

In a separate pot, bring water to a boil and add a pinch of salt. Cook egg noodles until al dente, about 7 minutes. Drain and rinse under cold water.

In the same skillet, lower the heat and add cream of mushroom soup, cream cheese, sour cream, milk, and garlic powder. Stir until the mixture is warm and smooth, about 5 minutes.

In a mixing bowl, combine cooked noodles, drained tuna, and creamy sauce. Mix gently until noodles are evenly coated.

Grease a 9x13 inch baking dish and pour in the tuna noodle mixture, spreading it out evenly.

Sprinkle shredded Colby Jack cheese and French fried onions over the top of the casserole.

Bake for about 10–15 minutes, or until the cheese is melted and bubbly and onions are golden brown.