How to Make It
Heat oven to 400° F. Finely chop the onion. Heat the oil in a medium skillet over medium heat. Add the onion and cook, stirring occasionally, until tender, 6 to 8 minutes.
While the onion cooks, chop the garlic and parsley. Add the garlic, parsley, and fennel seeds to the skillet and cook, stirring, for 1 minute. Remove from heat, transfer to a large bowl, and let cool for 5 minutes.
Line a rimmed baking sheet with foil or parchment paper.
Add the turkey, bread crumbs, egg, ½ teaspoon salt, and ¼ teaspoon pepper to the cooled onion mixture and gently mix to combine.
Wet your hands (this will keep the meat from sticking to them) and form the turkey mixture into balls about the size of a heaping tablespoon (make sure they are roughly the same size as the store-bought ones). You should get about 20 meatballs.
Place the meatballs on the baking sheet along with a few store-bought ones, spacing them 1 inch apart. Roast until they are cooked through, 18 to 22 minutes. You may have to keep an eye on the store-bought ones to make sure that they don’t overcook.
While the meatballs are cooking, bring a large pot of water to a boil for the spaghetti and warm the marinara sauce in a small saucepan over medium-low heat.
Cook the spaghetti.
Drain the spaghetti and place it in a large bowl or platter. Place the meatballs on a large platter or in a shallow bowl. Place the tomato sauce in a small serving bowl and do the same with the Parmesan.
Set all the separate platters and bowls on the dinner table. Sit down and have everyone, including the kids, serve themselves.