Cook hamburger with onion, drain. Add taco mix and water, cover and cook til no longer watery.
In casserole dish or shallow crock pot, spray with cooking spray. Place tortillas slightly overlapping around edges and bottom of dish.
Start layering. Spoon burger over tortillas, then picante sauce, cheese, tortillas, burger, sour cream, picante, Queso, tortillas, keep layering end with tortillas on top. Then cover with shredded cheese.
Bake at 400 degrees till cheese is melted OR heat in crock pot til cheese is melted. **You can layer in any order that you prefer.* I have found that first layer of meat becomes dry if the picante sauce isn't added to the first layer.