Fry the onions first. Slice them thin, toss with a little flour, and fry in hot oil until golden and crisp. Do not crowd the pan. Drain on paper towels and salt them immediately.

Cook the beef next. Pat it dry, season well, and sear in a hot pan with a bit of oil and butter until a good brown crust forms. Cook to your preferred doneness, then pull it out to rest.

Build the roast sauce in the same pan. Lower the heat, add a bit more butter if the pan is dry, then pour in the broth and scrape up the browned bits. Simmer until it tastes rich.

If you want the sauce thicker, whisk in a little cornstarch slurry. Taste and adjust salt and pepper.

Prepare Spätzle. If store-bought, warm it near the end. If making fresh, do that while the sauce simmers.

Assemble the dish: plate the Spätzle, place the beef on top, pour sauce over the meat, and finish with the fried onions.