Position a rack in the center of the oven and heat the oven to 400°F.
In a medium bowl, whisk the eggs and mix in the cheese.
Heat the olive oil in a well-seasoned 10-inch cast-iron skillet (or ovenproof nonstick skillet) over medium-high heat. Add the onions and cook, stirring frequently, until golden around the edges, 2 to 3 minutes. Stir in the artichoke hearts, parsley, 1/2 tsp. salt, and 1/4 tsp. pepper.
Remove from the heat and add the egg mixture. Stir just until the vegetables and herbs are distributed evenly. Transfer to the oven and bake until the eggs are set and firm to the touch, 13 to 14 minutes. Let the frittata rest in the pan for 2 minutes.
Run a knife or spatula around the edge of the pan to loosen the frittata and slide it out onto a cutting board. Slice the frittata into wedges and serve hot or at room temperature.
nutrition information (per serving):
Photo: Scott Phillips