Combine the oil and 2 tablespoons of the butter in a wide deep skillet or flameproof casserole, preferably nonstick, with a lid and place over medium-high heat.
Wait a couple of minutes and, when the butter foam subsides, add the veal shanks and brown them well, rotating and turning the pieces as necessary, 15 minutes or more.
Sprinkle the meat with salt and pepper as it cooks; when the meat is brown, transfer it to a plate.
Reduce the heat to medium, add the onion and carrot, and cook, stirring occasionally, until they soften, about 10 minutes.
Stir in the cardamom, then the cherries and their juice, along with the stock.
Bring to a boil and turn the heat to low.
Return the veal shanks to the pan and cover the skillet; adjust the heat so the mixture simmers steadily.
Cook until the meat is very tender and pulling away from the bone, at least 90 minutes and probably more; turn the veal every half hour or so.
(When the meat is tender, you may turn off the heat and refrigerate the dish for up to 24 hours; reheat gently before proceeding.)
If the sauce is thin, transfer the meat to a warm platter and turn the heat to high; boil the sauce until it becomes thick and glossy, about 5 minutes.
Stir in the remaining butter, a bit at a time, then add the lemon zest and turn off the heat.