1. Peel onions and slice into rings. Cut a shallow cross in rounded end of tomatoes, immerse briefly in boiling water, then skin and cut into segments, removing core.
2. Melt half the butter in a pan, brown onions, pour in white wine and cover, then simmer for about 5 minutes until done.
3. Add tomato segments to onions, cook over medium heat 5 minutes longer, uncovered, to thicken liquid slightly.
4. Wash and pat dry turkey livers, removing any fat or skin. Cut into strips and dust with flour.
5. Wash and dry sage.
6. Heat remaining butter in another pan and fry liver strips until they turn grey.
7. Add cooked liver to tomato sauce, seasoning with salt and pepper, and sprinkling with sage leaves.