Preheat Oven to 400°F.
Remove the top from the tomatoes and scoop out the inside, leaving enough room to keep the shell intact. Chop the pulp, place in a bowl and seat aside.
Sauté diced onion in 2 tbsp of olive oil until translucent, about 5 minutes.
Add minced garlic and sauté for about 1 minute, until fragrant.
Add the pulp of the tomatoes to the sautéed onions and cook until most of the water is evaporated, about 10 minutes. Season with salt and pepper.
Allow the cooked tomatoes to cool.
Toast the keto bread and shred with your hands, soak in water. Set aside.
Meanwhile, lightly toast the pine nuts in a small pan for about 3-5 minutes. Set aside.
Combine the cooled cooked tomatoes, ground pork, parmesan reggiano, keto bread, egg, pine nuts, parsley, nutmeg, salt and pepper.
Sprinkle a small amount of the mozarella inside the bottom of each tomato and add the filling. (Save most of the mozarella for later).
Place the stuffed tomatoes on a baking tray and bake for 45 minutes.
Remove the stuffed tomatoes from the oven and top with the remaining mozarella. Cook for another 10-15 minutes until the cheese is melted.
Serve immediatly and enjoy!