Put the flour in a large shallow platter and season it with a fair amount of salt and pepper. Get in the habit of always tasting your flour; once it coats the veal it is harder to adjust the seasoning. Dredge the veal shanks in the seasoned flour and then tap off the excess (extra flour will burn and make the dish off-tasting).
Heat a large Dutch oven over medium heat and hit it with a 3-count drizzle of oil. Add the butter and swirl it around the pan to melt. Sear the veal shanks, turning carefully with tongs, until all sides are a rich brown caramel color. Drizzle with a little more oil, if needed. (Do this in batches if the shanks are big and look crowded in the pot.) Remove the browned veal shanks to a side plate. There will be a lot of flavor left over in the bottom of the pot. You're going to use that to create your sauce.
Preheat the oven to 375 degrees F.
Using the same pot, saute the onion, celery, carrots, lemon zest, garlic, bay leaves, and parsley over medium heat. Cook the vegetables down until they start to get some color and develop a deep, rich aroma. Season with salt and pepper; add a little oil if needed. Nestle the veal shanks back in the pot. Pour in the wine and let it simmer down for 20 minutes, until the wine has reduced by half. Reducing is key for intense flavor. Add the beef broth and tomatoes and stir everything together. Cover the pot and put it in the oven. Braise for 1 and a 1/2 hours. Then remove the cover and continue to cook for another 30 minutes. The sauce should be thick and the veal tender and nearly falling off the bone.
Remove bay leaves.
For the gremolata:
Finely chop the pine nuts, dried cranberries and combine. Combine this with the garlic together in a mini chopper or with a mortar and pestle. Fold that into the orange zest and parsley. Scatter the gremolata over the Osso Bucco before serving.