Salads - Cabbage and watercress salad with sumac and onion

Recipe Ingredients:

- 1 kilogram of white cabbage, chopped- 4 cups of arugula- 2 tomatoes, chopped- 1 onion, chopped- 1 tablespoon of sumac- 1/4 cup of olive oil- 1/4 cup of vinegar- Salt and pepper