Drain and chop the tomatoes. Mix with the pesto. Form 4 dumplings from the dumpling dough with wet hands. Flatten the dumplings, spread the tomato mixture on them and form them into dumplings again.
Cook in boiling salted water at medium heat for 20-30 minutes. Melt butter. Fry breadcrumbs in it. Remove the dumplings, drain and spread the butter crumbs on top.