Sunday gravy is not a delicate dish. It has been on the stove for hours. There is tomato, which is sharp, and pork, which is rich, and usually someone has added a little sugar to calm the tomato down. The wine has to stand up to all of it.
The rule is simple: match the acid. Tomato is acidic, and a soft, round wine tastes flat next to it. You want a red with enough brightness to meet the sauce halfway.
The classic: Chianti Classico
Sangiovese grew up next to tomato. A Chianti Classico, or a Riserva if the pot has ribs and sausage in it, has the acidity for the sauce and the fruit for the meat. If you only buy one bottle for the table, buy this one.
For a heavier pot: Montepulciano d'Abruzzo
When the gravy has braciole and meatballs and the whole family is coming, go darker. Montepulciano d'Abruzzo is generous, a little rustic, and rarely expensive, which matters when the bottles keep getting opened.
The surprise: a dry Lambrusco
Cold, dark, a little fizzy, and dry. Look for Grasparossa on the label. The bubbles cut through the fat, and it makes a long lunch feel lighter than it is.
Pour it when the sauce goes on, not when it comes off. The cook deserves a glass too.
One more thing: serve the red a little cool, around sixty degrees. A warm red next to a hot plate tastes like alcohol. Ten minutes in the fridge fixes it.