Rub the slow cooker with a little oil to avoid sticking. Place the chicken breasts in it and pour the salsa over them. Cook on high for about 3 to 3 ½ hours, on automatic for about 5 hours.
Only at the very end add the cumin, the chilli powder and the lemon juice and simmer for another 15 minutes before serving.
Delicious with a green salad and on a sandwich or with very old-fashioned fried potatoes.