Preheat the oven to 350 degrees.
Add the ground beef to a skillet and brown over medium heat, chopping as it cooks, until all of the meat is browned. Drain grease.
While the meat is cooking, dice the tomato, and cliche the green part of the onion.
Grease the cavities of a muffin tin, and set the wonton wrapper inside, gently pressing to the sides to form a bowl.
Stir the taco seasoning into the meat mixture, and divide evenly between the wonton cups.
Bake for 10-12 minutes.
Remove from the oven, and top with sour cream, cheese, tomatoes, and onion.