remove coarse outer leaves of cabbage. cut cabbage lengthwise into fourths, and then core the sections. now cut each quarter into fine, thin shreds (or use food processor).
put oil in wide, nonstick pan and set over medium-high heat. when oil is hot, add cumin, fennel, and sesame seeds. as soon as sesame seeds begin to pop, add onion. stir and fry for 3-4 min or until onion begins to brown. add cabbage. stir and fry for 6 min or until cabbage browns. add salt and cayenne.
turn down heat to medium low and cook, stirring periodically, for another 7-8 minute or until onions appear carmelized and soft. add lemon juice and garam masala and stir to mix.