Preheat the oven to 375°F.
Bring a large pot of salted water to a boil. Cook the quinoa spaghetti according to package directions. Do not overcook. Drain and set aside.
To make the meatballs, soak the bread in the milk in a small bowl. Set aside.
Combine the ground turkey, garlic, grated onion, parsley, egg, cheese, salt and pepper in a large bowl. Remove the bread from the milk and squeeze out any excess liquid. Break the bread up into small pieces and add it to the turkey mixture. Mix to combine being careful not to overmix the meat. Form the meat into approximately 16 meatballs, about 1 ½ inches in diameter. Place the meatballs on a lined baking sheet and bake in the oven for 20-25 minutes.
While the meatballs are baking, make the tomato sauce. Heat the olive oil in a large saucepan over medium heat. Add the onion and cook until softened, 6-8 minutes. Add the garlic and tomato paste and cook until fragrant, another 2-3 minutes. Add the crushed tomatoes, salt, pepper, sugar, red pepper flakes, and oregano and stir to combine well. Simmer while the meatballs are baking.
When the meatballs are done, remove them from the oven and add them to the sauce. Cover the pan and simmer them in the sauce about 15 minutes, until they are completely cooked through. Stir in the fresh basil. Taste and adjust seasoning as desired.
To serve, toss the cooked spaghetti with the tomato sauce and place in a large serving bowl. Arrange the turkey meatballs on top. Garnish with sprigs of fresh basil. Serve with crusty Italian bread and Parmigiano-Reggiano cheese on the side.