Cut each pepper lengthwise along the creases, remove the stem, seeds, and pithy core, then peel with a swivel-blade vegetable peeler. Cut the peppers into strips slightly less than 1" wide.
Pour the olive oil into a 12" skillet, preferably nonstick. Add the garlic cloves, turn the heat on to medium-high, and cook the garlic, turning it from time to time, until it becomes colored a light nut brown. Remove from the pan and discard.
Add the peppers with a pinch or two of salt and turn the heat down to medium. Cook the peppers, turning them over from time to time, until they are quite tender. It should take about 45 minutes, and they will be wilted and considerably diminished in bulk.
While the peppers are cooking you can move forward with other steps of the sauce. Skin the tomatoes using the swivel-blade vegetable peeler. (Don't skin them by scalding them in hot water, because you want them to be very firm.) Chop them coarsely.
Pour the vegetable oil into a 10" skillet and add the butter and chopped onion. Turn the heat on to medium-high and cook the onion, stirring from time to time, until it becomes colored a pale gold.
Add the ground veal with some salt and liberal grindings of black pepper and turn the heat down to medium. Cook the meat, turning it once or twice, until it has completely lost its raw color. Add the tomatoes with any of their juice, then turn the heat down some more to cook at a gentle simmer for about 20 minutes.
When the peppers are done, transfer the contents of the skillet with the veal to the pan with the peppers, turning all the ingredients over two or three times to coat them well. Cook at a gentle simmer for 15 minutes, stirring from time to time. Taste and correct with salt.
Cook the pasta in 4 quarts of rapidly boiling salted water. The instant it is done al dente, tender yet firm to the bite, drain it and transfer it to a warm serving platter or bowl. Pour the sauce over it. Toss quickly and thoroughly, add grated parmesan, and toss again. Serve at once.