You’ll Need

8 ounces spaghetti broken in half
1 tablespoon butter
1 onion finely diced
1 green bell pepper diced
8 ounces white mushrooms diced
16 ounces boneless, skinless chicken breast cut into bite-sized pieces
15 ounces canned petite diced tomatoes drained well
1 teaspoon Italian seasoning
1 teaspoon kosher salt
pepper to taste
1/2 cup low-fat plain yogurt
1/2 cup cheddar cheese shredded
1/4 cup Parmesan cheese grated
1 cup mozzarella cheese shredded
paprika (optional)

Directions

Preheat oven to 350 degrees F. Spray an 8×11″ baking dish with cooking spray. (You can use a differently shaped medium-sized baking dish if you don’t have this size available.)
Cook broken spaghetti according to package directions. Drain and set aside.
While pasta cooks, melt butter in a large skillet over medium-high heat. Add onion, bell pepper, mushroom, chicken, tomatoes, Italian seasoning, salt, and pepper. Cook, stirring often, until vegetables are tender and chicken is cooked through. Keep heat fairly high so most of the liquid cooks off in this step.
Stir yogurt, cheddar cheese, and parmesan cheese into chicken mixture until well combined. Stir in cooked spaghetti until well coated. Pour pasta into baking dish. Spread mozzarella over the top, and lightly sprinkle with paprika and Italian seasoning if desired.
Bake in preheated oven for 25-30 minutes or until cheese is melted and bubbly.

Notes
I chopped the vegetables in my food processor to make them really teeny (and because I’m kinda lazy), but of course you can chop them by hand if you are so inclined.
I listed this as six servings, but that’s if some of the servings are for kids. It may not be enough to feed six hungry adults.
You can use all mozzarella or all cheddar cheese in this recipe if you prefer.