Sprinkle 1 tablespoon of the taco seasoning over the meat and gently mix. Set aside while prepping other ingredients.
Heat the vegetable oil in a 4-5 quart Dutch oven or soup pot over medium heat until the oil shimmers on the surface.
Add the meat, using a spatula to distribute it evenly across the surface, for fastest cooking. Stir frequently, breaking up the big chunks as you go.
When the meat has mostly browned (about 5 minutes), check the pot for excess grease/fat. Drain or spoon out and discard if there is more than about a tablespoon.
Add the onions to the pot and continue stirring.
When the meat is fully browned, add the tomato paste and the remaining 1 tablespoon of taco seasoning, mixing thoroughly.
Add the Rotel, the corn, and the broth, and increase heat to medium-high.
Bring the broth to a gentle boil, then lower heat to medium or medium-low to maintain a gentle simmer. Cook for 10 minutes and reduce heat to low.
Combine the cream and sour cream in a small mixing bowl. Remove a ¼ cup of hot broth from the soup and whisk into the cream until combined. Then pour the mixture into the soup.
Taste the soup and add more salt as needed. (Add small amounts, stir, and taste again.)
Stir the green onions and cilantro into the soup, and serve with your favorite toppings.
