Let the roast sit at room temperature for 30 minutes. Position a rack in the middle of the oven and heat the oven to 400°F. Put a roasting rack in a roasting pan or a heavyduty rimmed baking sheet. (Line the pan with foil for easier clean-up, if you like.)
Season the veal liberally with salt and pepper on all sides. Turn on the exhaust fan. Heat the oil in a 12-inch skillet over medium-high heat. When the pan is very hot, brown the meat on all sides, including the ends, about 3 minutes per side. Transfer the meat to the roasting rack, meaty side up. Set aside to cool while you prepare the crust.
Purée the red onion, capers, lemon juice, mustard, and egg in a food processor. The mixture will be fairly loose.
In a small bowl, stir the breadcrumbs, tarragon, Parmigiano, scallions, and lemon zest. When the veal is cool enough to touch, pour the onion purée over the meat, using a spatula to spread it evenly. Some of the mixture will spill off the roast and into the pan—that’s fine. Pat the breadcrumb mixture into the onion purée on the top and sides of the rack of veal, pressing slightly to help the crust adhere.
Roast the veal until an instant-read thermometer inserted into the thickest part of the meat reads 125° to 130°F for medium rare, 55 to 90 minutes, depending on the size of the rack. (To keep the crust from overbrowning, start checking on the roast after 30 minutes of cooking; when the crust is golden brown, tent it with a sheet of aluminum foil.) While the veal is roasting, prepare the rémoulade.
Remove the veal from the oven and let rest for 10 minutes (it will continue to cook as it rests) before carving into single chops and serving with the rémoulade. Don’t fret if some of the crust falls off the meat when you carve.
Try a bright, intensely flavored Italian red, such as a Barbera or a Chianti Classico Riserva. Both will mirror the acidity in the lemon juice as well as the flavors of the fresh herbs.