In a food processor, place the onion, garlic, herbs, and kale and pulse until very finely chopped. Transfer the mixture to a large mixing bowl and add the ground turkey, sea salt, black pepper, and 1 tbsp olive oil. Use your hands to combine.
Roll the mixture into golf ball-sized meatballs. They will be sticky so just do your best to make a round shape. Heat the additional 4 tbsp olive oil in a large nonstick skillet over medium-high heat. Cook the meatballs until they are browned all over.
Add the tomato sauce to the pan and partially cover the pot. Let the meatballs cook gently for 1/2 hour, carefully stirring every now and then.