How to Make It
Preheat oven to 425°F. Cut off top 1 1/2 inches of asparagus, and cut stalks into 1/4-inch pieces. Cut onion bulbs into quarters; cut stalks into 1/4-inch pieces. Toss together asparagus tips, onion bulb quarters, 1 tablespoon of the oil, and 1/4 teaspoon of the salt in a bowl. Spread evenly on a baking sheet lined with parchment paper; roast in preheated oven until onions begin to brown and asparagus is bright green and tender, 12 to 15 minutes, turning once halfway through. Set aside. Reduce oven temperature to 375°F.
While asparagus mixture roasts, heat remaining 1 tablespoon oil in a 10-inch cast-iron skillet over medium. Add cut asparagus stalks and onion stalk pieces; sprinkle with 1/4 teaspoon of the salt. Cook, stirring occasionally, until onions are soft and asparagus is bright green and tender, 4 to 5 minutes. Remove from heat. Spread stalk pieces in an even layer. Sprinkle 1 1/3 cups of the cheese on top, and let it start to melt.
Whisk together eggs, cream, crème fraîche, parsley, chives, pepper, and remaining 1/2 teaspoon salt in a small bowl. Pour over mixture in skillet; scatter top with asparagus tips and onion bulbs.
Cook over low until eggs start to set on side of skillet, 7 to 8 minutes. Sprinkle with remaining 1/3 cup of cheese. Place skillet in oven, and bake at 375°F until eggs are fully set, 12 to 14 minutes.
Cool in skillet 5 minutes; slice into wedges and serve.