To make the meatballs: Combine all ingredients in a large bowl and mix until well combined. Form meatballs by scooping about two tablespoons of the mixture and using your hands to roll into balls. Continue until all meatballs are formed.
Heat a large skillet to medium-high heat. Add all the meatballs to the skillet and cook for about 10 minutes, stirring the meatballs around every few minutes to ensure an even cook.
Add diced tomatoes and tomato sauce to the skillet with the meatballs and gently stir to coat all the meatballs in sauce. Turn heat down to low. Cover and cook for about 10 more minutes to let flavors of the meatballs to fully develop into the sauce.
While the meatballs are cooking; boil the spaghetti according to the package instructions.
Serve meatballs over spaghetti and top with red pepper flakes and parmesan cheese(optional). Enjoy!