Between two sheets of plastic wrap, pound the veal lightly to get it as thin as possible. Don't let it break through.
Coat the veal slices lightly on both sides with some of the olive oil. Season with salt and set aside.
Heat the remaining olive oil in a skillet over medium-high heat. When it shimmers, add the onion, crushed red pepper and garlic. Cook until the garlic is fragrant--about a minute.
Add the remaining ingredients except the butter and bring to a light boil. Hold at a light boil for ten seconds (only!), then remove from the stove. The sauce will seem too runny and unfinished, but that's how you want it.
Whisk the butter into the sauce and set aside, but keep it warm.
Put the veal paillards on the preheated grill or broiler rack. When the veal has browned in spots--turn it over and cook the other side a little less than the first side. This will take less than a minute total--perhaps less than 30 seconds. Don't overcook or the veal will be tough!
Place the veal on pre-warmed plates and spoon some of the sauce over it.