Melt the butter in a soup pot over low heat. Add the onions and cook, covered, until tender, about 20 minutes. Add the garlic and cook for another 5 minutes.
Add half of the dill, season with salt and pepper, and cook, uncovered, for another 15 minutes.
Add the chicken stock, tomatoes, allspice, and a pinch of sugar. Bring to a boil, reduce the heat,