In a 12-inch skillet, heat 2 tablespoons of the oil over medium-high heat. Add onion and garlic; cook 3 to 4 minutes, or until softened, stirring occasionally. Remove from heat and set aside.

In a large bowl, combine beef, eggs, bread crumbs, parsley, salt, pepper and the onion mixture; mix well. Form into 18 balls.

In the same skillet, heat remaining 3 tablespoons oil over medium heat. Add the meatballs and cook 15 to 20 minutes, or until beef is no longer pink inside, turning occasionally.

While the meatballs are cooking, prepare spaghetti according to package directions; drain. Arrange on a serving platter and cover with aluminum foil to keep warm.

When meatballs are cooked, arrange them on top of the spaghetti. Add lemon juice to the skillet and stir to scrape drippings from the bottom of the pan; pour over meatballs and spaghetti. Spiinkle meatballs with parsley and lemon peel, if desired, and serve.