Start by preheating your oven to 350°F (175°C). Grease your muffin tin with a little olive oil or line it with muffin liners for easy removal.
In a skillet over medium heat, add 1 Tbsp of olive oil. Once hot, add the chopped yellow onion and sauté for about 2-3 minutes until translucent. Then, add the minced garlic and sauté for another minute until fragrant. Stir in the shredded zucchini and chopped red bell pepper, cooking for an additional 3-4 minutes until the veggies are tender. Remove from heat and set aside.
In a large mixing bowl, crack all 8 large eggs. Whisk them together until well beaten. Season with salt and pepper to taste.
Add the sautéed vegetable mixture to the bowl with the beaten eggs. Toss in the roughly chopped arugula and shredded Parmesan cheese. Stir everything together until well combined.
Using a ladle or measuring cup, pour the egg and veggie mixture evenly into the prepared muffin tin, filling each cup about ¾ full.
Place the muffin tin in the preheated oven and bake for 18-20 minutes, or until the muffins are puffed up and a toothpick inserted into the center comes out clean.
Once baked, remove the muffin tin from the oven and let it cool for a few minutes. Carefully run a knife around the edges of each muffin and gently pop them out. Enjoy warm or allow them to cool completely before storing.
