Stir the soup, sour cream, picante sauce and chili powder in a medium bowl.
Stir 1 cup picante sauce mixture, chicken and cheese in a large bowl. Divide the chicken mixture among the tortillas. Roll up the tortillas and place them seam side down in an 11 x 8" shallow baking dish. Pour the remaining picante sauce mixture over the filled tortillas. Cover the baking dish.
Bake at 350 degrees for 40 minutes or until the enchiladas are hot and bubbling. Top with the tomato and onion.
**I like Salsa Verde (green salsa) and sometimes pour that over the top and add some additional cheese over top, as these pictures show.