Preheat oven to 350 degrees Fahrenheit.

Grease a 9-inch glass pie plate with cooking spray.

Melt butter in a 12-inch nonstick skillet over medium heat.

Add spinach and bell pepper to the skillet.

Cook for about 5 minutes, stirring occasionally, until spinach is wilted and bell pepper is crisp-tender.

In a small bowl, whisk together milk, flour, salt, nutmeg, and eggs until smooth.

Pour the egg mixture into the skillet with the spinach and bell pepper.

Stir to combine.

Pour the mixture into the prepared pie plate.

Bake uncovered for about 30 minutes, or until the center is set.

Sprinkle with grated parmesan cheese.

Serve warm.