In a large pot pour both cans of tomatoes plus 2 cans full of water. Bring to a boil over medium high heat then reduce to low to simmer. Meanwhile chop onion and saute in a Tbs of olive oil until softened (about 5 min). Stir onion and basil into tomatoes. Scoop sour cream into a a medium bowl and add a ladle full of hot tomato liquid to it and stir until combined. Add one to two more ladles full and then pour mixture into tomatoes. Sir to combine. Stir in the cheddar cheese until melted. Remove from heat and enjoy!

*Its important not to add sour cream directly to hot liquid as it will separate and clump up.