Preheat oven 400 degrees
Put rack in middle of oven
2
Whisk eggs
3
In a 10-inch ovenproof nonstick skillet, heat water/chicken broth and cook onion over medium heat until shimmering. Add onion and cook, stirring, until it begins to soften, 4 minutes. Add broccoli and cook, stirring, until warmed through, 2 minutes more.
4
Pour eggs over vegetables, covering them evenly; cook, gently lifting and pushing cooked edges toward center, allowing liquid egg to fill space, about 4 minutes. Sprinkle with cheese and transfer pan to oven. Bake until frittata is golden brown and puffed up, 12-15 minutes (frittata should be just slightly soft in center). Transfer frittata to a cutting board, cut in 6 wedges and serve immediately.
