In a large mixing bowl, combine the ground turkey, fennel seeds, 1 teaspoon of black pepper, salt, Parmesan cheese, minced garlic, panko breadcrumbs, egg, minced onion, and parsley. Use your hands to mix everything together until just combined. Be careful not to overmix, as this can result in dense meatballs.
Once the mixture is well combined, use a spoon or an ice cream scoop to portion out the meatballs. Aim for roughly 1 to 1.5 inches in diameter. Place them on a baking sheet lined with parchment paper or directly into a skillet with a bit of olive oil.
In a skillet over medium heat, add a touch of olive oil. Once hot, add the meatballs in batches to avoid overcrowding. Cook for about 5-7 minutes on each side, or until they are golden brown and cooked through. Alternatively, you can bake them in a preheated oven at 375°F for approximately 20-25 minutes.
In a large pot, pour in the marinara sauce and add the remaining 1/2 teaspoon of black pepper and crushed red pepper flakes. Stir to combine and let it simmer on low heat for about 10 minutes, allowing the flavors to meld together.
Once the meatballs are cooked, gently place them into the simmering marinara sauce. Allow them to soak up the sauce for an additional 5 minutes. Serve hot, garnished with more fresh parsley if desired.
