Slice the chicken breast into two equal thin pieces. Cut one or two red onions into long slices and put them aside.
Mix all seasonings (including all-purpose flour) in a plastic zip-lock bag or a bowl. Coat the seasonings mixture thoroughly on the chicken pieces.
Fry marinated chicken breast pieces in a frying pan with medium-high heat. You don't need to cook deeply. We aim at giving a light brown colour to the chicken pieces.
Load in the slow cooker. Add a layer of sliced onions on the bottom and then take those browned chicken breast pieces and load them over the onions in the slow cooker.
Squeeze a lemon on the chicken once you load it into the cooker. This step is totally optional. However, you can add ⅓ cup of lemon juice to give the chicken a good sour taste.
Pour in some chicken broth to prevent the meat from drying out. Make sure the chicken broth is just slightly to cover the chicken breast. Adding too much liquid will overcook the chicken.
Cover the lid of your slow cooker and set the temperature. Let it get cooked on High for around 4 hours or on Low for 6 hours.
After hours, you can take the chicken out and serve it on a plate with all those onions.