Wash and remove tendons from the beef, cut into 1.5–2 cm thick slices across the grain, pound each slice to 0.5–1 cm thick, then cut into strips.
Cut 2 onions into half rings, heat 40 ml vegetable oil in a large frying pan over medium-high heat, add the onions and fry for 3–4 minutes, stirring occasionally, until translucent.
Season the beef strips with 0.5 teaspoon salt and 0.5 teaspoon ground pepper, add to the pan, and fry over high heat for 5–6 minutes, stirring constantly, until the meat is no longer pink.
Sprinkle 30 grams wheat flour over the meat, stir thoroughly to combine, and fry for 2–3 minutes over medium-high heat.
Stir in 250 grams sour cream, reduce heat to medium-low and simmer for 2–3 minutes, transfer to a serving plate and top with fresh dill and parsley.