Cook the pasta according to the label until al dente. Reserve 3 TBSP cooking liquid; drain.
Meanwhile, in a large bowl, combine the turkey, flaxseed, Parmesan, egg, pepper, and 1/2 tsp salt. Mix well, then shape into 8 equal meatballs.
Heat 1 TBSP oil in a large skillet over medium heat. Arrange the meatballs in a single layer in the skillet, working in batches if necessary. Cook, gently turning the meatballs occasionally, until golden brown on all sides (about 10 minutes). Transfer the meatballs to a dish.
Heat the remaining TBSP oil in the same skillet. Reduce the heat to low. Add the garlic and cook, stirring, until golden and aromatic (1-2 minutes).
Add the tomatoes and crushed red pepper. Stir until well mixed. Raise the heat to medium-high.
Add the browned meatballs and remaining 1/2 tsp salt. Cook, stirring occasionally, until the meatballs are cooked through and the sauce thickens slightly (about 10 minutes).
Add the pasta and the reserved cooking liquid to the meatball mixture. Gently toss until well combined. Serve hot.