Heat oil in a skillet then add diced onion and minced garlic. Allow to cook for 2-3 minutes then add ground beef. Season with taco seasoning and cook ground beef until browned.
In a separate pot cook spaghetti according to the package directions. When fully cooked drain and return to the pot. Add seasoned ground beef and Rotel to spaghetti and mix together well.
Preheat oven to 375 degrees F. Add spaghetti to a casserole dish. Top with cheese and place in the oven for 10 minutes until cheese is melted and bubbly. Top with cilantro and serve!