Put the chicken pieces into salted water and cook, covered, until tender, about 30-35 minutes.
Meanwhile peel and dice the tomatoes (skip this step for tinned tomatoes), then cook them soft in a little water, and purée through a sieve or with an immersion blender.
Make a light roux from the butter and the flour, then mix it smooth with cold water so it doesn't go lumpy.
Add the roux to the tomato purée, bring to a boil, and pour in enough of the chicken's cooking liquid to get the amount of soup you need.
Add the cooked chicken to the tomato broth, bring to a boil, season with salt to taste, and round off the acidity with a pinch of sugar.
Serve drizzled with cream or sour cream.
Based on: Malatinszky Fanny szakácskönyve (a classic Hungarian cookbook), modernised. Calories and protein are estimated.