Shuck corn and cut kernels off the cob; dice bell pepper and onion. Heat olive oil over medium-high heat in a Dutch oven until shimmering, then add the corn, onion, and bell pepper. (Careful! The corn will want to splatter.)
Saute for two minutes, then stir in garlic and continue to saute over medium-high heat for about eight more minutes until pepper and onion are softened, stirring occasionally.
Stir in the vegetable broth, tomato paste, and spices, and bring to a boil. Reduce heat to low and simmer for 20 minutes, stirring occasionally.
Stir in the cheese and sour cream until melted and incorporated into the soup.
Serve hot, garnished with optional green onions if desired.