Peel and finely chop the onion. Wash the meat, dab dry and cut into strips. Wash the asparagus and cut off the woody ends generously. Cut the asparagus into pieces. Clean and wash the mangetouts.
Wash the tomatoes. Wash lemon hot, dry and grate the peel finely. Halve the lemon and squeeze one half.
Cook the asparagus in 3⁄4 l boiling salted water for 3-4 minutes. Add sugar snap peas, continue cooking for 1 minute. Pour off and drain, collect 600 ml of boiling water.
Heat the oil in a large frying pan. Brown the meat in it thoroughly. Fry the onion and tomatoes briefly. Season with salt and pepper. Dust with flour and sauté. Stir in cooking water and lemon peel, bring to the boil and simmer for about 5 minutes.
Stir in sour cream. Fold in the asparagus and mangetouts and heat up again. Season with salt, pepper, 1 pinch of sugar and lemon juice. If you do not want to eat low-carb, you can cook rice with it.