Prep the Vegetables: Slice the mushrooms, zucchini, and red onion. Mince the garlic and set everything aside.

Sauté the Vegetables: Heat 1 tablespoon of olive oil (or butter) in a non-stick skillet over medium heat. Add the red onion, mushrooms, and zucchini, and cook for 3-4 minutes until softened. Stir in the minced garlic, balsamic vinegar, Italian seasoning, and red chili flakes. Cook for another 1-2 minutes, then transfer the mixture to a plate.

Beat the Eggs: In a small bowl, whisk the 4 eggs with a pinch of salt and black pepper until well combined.

Cook the Omelet: Wipe the skillet clean, then heat it over medium-low with a small drizzle of oil or butter. Pour in the beaten eggs and let them cook undisturbed for about 1-2 minutes, until the edges start to set.

Add the Filling: Spread the sautéed veggie mixture over one half of the omelet. Sprinkle the grated Parmesan cheese on top of the veggies.

Fold and Finish: Use a spatula to gently fold the other half of the omelet over the filling. Cook for another minute, letting the cheese melt and the eggs fully set.

Serve: Slide the omelet onto a plate, garnish with extra Parmesan or chili flakes if desired, and enjoy warm!