This sauce is intended for Spit-Roasted Chicken, but it's just as delicious served alongside grilled venison and pheasant sausages, grilled Bartlett pears, and cabbage.
Heat olive oil in large saute pan set over medium heat. Add the garlic, and cook until golden, about 3 minutes. Add the tomato sauce, and bring to a simmer.
Add quinces, sugar, vinegar, jalapeno, cinnamon, salt, lemon juice, and grappa, if using. Cook, stirring occasionally, until sauce thickens and quinces are soft and slightly broken down, 50 to 60 minutes. Store in an airtight container, refrigerated, up to 5 days.
You can also use firm, but not hard, Bartlett pears in place of quinces.