Heat 1 tablespoon olive oil in a large skillet over medium high heat. Add garlic and onion, and cook until translucent and sweet, around 7 minutes. Transfer to slow cooker.
Heat remaining tablespoon of oil in the same skillet and increase heat to high. Add beef and cook until browned. Transfer to slow cooker.
Return skillet to the stove, turn the stove down to medium heat, and add red wine. Bring to simmer and scrape all the brown bits off the bottom of the skillet into the wine, then pour the mixture into the slow cooker.
Add remaining ingredients, except for spaghetti, into the slow cooker and cook on low for 6 hours.
After sauce has cooked, bring a large pot of water to a boil and cook spaghetti according to package instructions. Reserve ½ cupof pasta water, and then drain the noodles.
Add the pasta back to the pot, along with the reserved pasta water and the pasta sauce. Toss gently and cook over medium-high for2 minutes or until the sauce has thickened.
