1. In a medium saucepan over high heat, bring chicken broth to a boil.
2. Add onions and rice.
3. Reduce heat to low.
4. Simmer, covered, for 12 minutes.
5. Meanwhile bring a large pot of water to a boil.
6. Add cabbage and boil for 2 minutes.
7. Drain.
8. Add cabbage and lemon slices to the broth/rice.
9. Simmer for 5 minutes.
10. Add chicken, parsley, salt, white pepper and cayenne.
11. Simmer until the chicken is heated.
12. Stir in the cornstarch mixture.
13. Return soup to a simmer.
14. Serve hot.