Prepare spaghetti noodles according to package directions. Drain, return to pot and drizzle with one tablespoon of olive oil. Toss so they don't stick one to each other.
In the meantime, place a large skillet or cast iron pan over medium-high heat and add 2 tablespoons of olive oil.
Once the oil is hot and meat, and do not move it for 1 minute, to get a nice sear on it. Start crumbling the meat, using a wooden spoon and cook the meat until nicely browned and no longer pink. Drain excess fat if needed.
Add chopped onion, minced garlic, tomato paste, salt, pepper and taco seasoning. Stir to combine and cook for about 2 minutes, until onion is soft.
Add spaghetti sauce and cook until warmed.
Add beef sauce to spaghetti noodles or add the noodles to the skillet if the skillet is large enough, mix thoroughly.
To assemble the tacos, fill the shells with spaghetti and garnish with desired toppings. Serve immediately.
Nutritional information does not include toppings.