Begin by bringing a large pot of salted water to a rolling boil. Add 12 ounces of elbow macaroni and cook according to the package instructions until al dente, usually around 8-10 minutes. Once done, drain thoroughly and set aside.

In a medium saucepan, melt 2 tablespoons of butter over medium heat. Add 2 tablespoons of all-purpose flour, whisking continuously for about 1-2 minutes until the mixture turns a light golden color.

Gradually pour in 2 cups of milk while whisking to prevent lumps from forming. Keep the heat at medium and stir consistently for about 5 minutes or until the mixture thickens.

Stir in 1 cup of shredded mozzarella, 1 cup of shredded sharp cheddar, and ½ cup of grated Parmesan cheese until all cheeses melt smoothly into the sauce.

Mix in 1 teaspoon of garlic powder, 1 teaspoon of Italian seasoning, and add salt and pepper to taste. Fold in 1 cup of chopped fresh spinach and ½ cup of chopped sundried tomatoes.

Add the cooked pasta to the cheese sauce, gently stirring until each macaroni is coated. Ensure all pasta is evenly mixed.

Transfer the mixture to a greased baking dish and bake in a preheated oven at 350°F (175°C) for about 15-20 minutes until bubbly and golden on top, or serve immediately.