Preheat the oven to 400ºF. In a small bowl combine the olive oil, minced garlic, Italian seasoning, and salt.
Slice each eggplant in half lengthwise, then use a paring knife to score a crosshatch pattern into the flesh (do not pierce the skin). Drizzle the seasoned olive oil over the cut surfaces of the eggplant and smear it around with the back of a spoon.
Place the eggplant on a baking sheet, cut sides down, and transfer the baking sheet into the oven. (Coat the baking sheet with non-stick spray for easy cleanup) Roast the eggplant for about 60 minutes, or until they look deflated and the skins appear wrinkly.
While the eggplant are roasting, prepare the meat sauce. Add the ground beef and olive oil to a sauce pot and cook over medium heat until the meat has browned. If using a higher fat content beef (90% lean or lower), drain the excess fat from the pot.
Dice the onion and add it to the browned beef along with the butter. Sauté over medium heat until the onions are soft and transparent. Add the crushed tomatoes, Italian seasoning, and some freshly cracked pepper. Stir to combine, then allow the sauce to come to a simmer. Once it reaches a simmer, turn the heat down to low and let it simmer until the roasted eggplant are finished, or for a minimum of 30 minutes. Before serving, taste the sauce, and add salt as needed (about 1/2 tsp).
When the eggplant are finished roasting, carefully flip them with a spatula (they will be quite soft). Top each eggplant half with a generous ladle of the meat sauce and a dusting of grated parmesan. Serve immediately.