Heat the olive oil in a skillet over medium heat and sauté the diced onion and 2 tbsp minced garlic until softened and fragrant, about 3-4 minutes. Transfer to a large bowl and let cool slightly. Add the ground turkey, egg, fresh parsley, fresh basil, salt, and black pepper to the bowl with the cooled aromatics. Mix gently with your hands until just combined—don't overmix, as this keeps the meatballs tender. Form the mixture into 1.5-inch balls and place them directly into your crockpot. I prefer to work with slightly damp hands when forming meatballs; it prevents sticking and gives them a more uniform shape.

In a bowl, whisk together the crushed tomatoes, diced tomatoes, 1.5 tbsp minced garlic, dried parsley, dried basil, dried oregano, onion powder, salt, black pepper, and red pepper flakes. Pour this sauce over the meatballs in the crockpot, gently stirring to coat them evenly. Cover and cook on high for 4 hours or on low for 6-8 hours. The meatballs are done when they're cooked through and the sauce has thickened slightly. I like to use Cento crushed tomatoes specifically because they have a naturally sweeter, less acidic flavor that balances beautifully with the lean turkey.

Ladle the meatballs and sauce over cooked pasta, rice, or roasted vegetables. For the best presentation, let the meatballs rest in the sauce for a few minutes before serving so they stay moist and flavorful.