Preheat your oven to 375°F (190°C).

In a medium-sized bowl, whisk together the eggs, heavy cream, grated cheddar cheese, salt, black pepper, and garlic powder until well combined. Set aside.

Heat the olive oil in a large oven-safe skillet over medium heat. Add the diced onions, bell peppers, and mushrooms. Sauté until the vegetables are softened and slightly golden, about 5-7 minutes. Add the arugula and cook for an additional 2 minutes until wilted.

Pour the egg mixture over the sautéed vegetables in the skillet. Gently stir the mixture to distribute the veggies evenly.

Cook the frittata on the stovetop over medium heat for 3-4 minutes, or until the edges start to set.

Transfer the skillet to the preheated oven and bake for about 15-20 minutes, or until the frittata is set in the center and the top is golden brown.

Remove the skillet from the oven and let the frittata cool for a few minutes. Slice into wedges, garnish with fresh herbs if desired, and serve warm.