Preheat oven to 350 degrees Fahrenheit.

Place pistachios, onions, salt, and pepper in a food processor and pulse until the mixture resembles crumbs. (Or place in plastic bag and crush using a meat pounder.) Set aside.

Rinse meat and pat dry. Season with salt and pepper. Heat a nonstick skillet. Grease (you’ll need just a bit of oil) and add veal. Pan-sear the veal, about five minutes per side.

Transfer the meat to a baking pan and allow to cool for several minutes.

Spread a thin layer of mayonnaise on the meat and then coat it with a thick layer of the pistachio mixture. Cover and bake for an hour and a half. Uncover and bake for an additional 30 minutes.

Heat oil in a saucepan over medium heat. Add onion and sauté until translucent, about seven minutes. Add tomatoes and cook for 10 additional minutes. Blend, using an immersion blender. Add sugar, salt and pepper. Simmer for an additional 10 minutes.

Meanwhile, prepare the squash. Heat oil in a sauté pan over medium heat. Add onions and sauté for 10 minutes. Add squash and sauté, stirring occasionally, for an additional 10 minutes. Add tomato sauce to cover squash, and cook over low heat for one hour.