Bring a large pot of water to a boil. Add the spaghetti and cook according to the package instructions. Once done, drain the pasta, reserving some of the pasta water for later use in the sauce. Set the cooked pasta aside.
Heat olive oil in a large pan over medium heat. Add the chopped onion and sauté for about 6 minutes, or until the onion becomes soft and translucent.
Add the ground beef to the pan with the onion. Season with salt, pepper, and garlic powder. Use a wooden spoon to break the beef into smaller pieces. Cook for about 10 minutes, stirring frequently, until the beef is browned and fully cooked.
Add the finely chopped carrots to the pan and sauté for 1 minute, allowing them to soften slightly.
Pour in the marinara sauce and add the reserved pasta water. Stir to combine. Adjust the sauce's consistency by adding more pasta water if you prefer a thinner sauce, or less if you want it thicker. Stir well to mix everything together.
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