Cut squash in half, lengthwise; remove seeds.  Place each half, cut side down, in large shallow covered pan(s).  Add water to depth of 2" and boil, covered, for 30 minutes.  Drain, then run fork over inside of squash shell to separate spaghetti-like strands from inner squash cavity in continuous passes.  Place shreds in strainer and allow to drain; set aside.  Liquefy garlic, ginger and water in food processor/blender; set aside. 
Heat oil in large pan over medium-high; add fennel and cumin seeds and stir
briskly until seeds begin to pop; reduce heat to medium.  Add onion and stir
together until onion begins to brown (5-6 minutes).  Add cayenne, turmeric and coriander and stir together until fragrant (10-20 seconds).  Add tomatoes, salt and sugar and stir together quickly; blend in reserved garlic-ginger mixture and spaghetti squash.  Transfer to oven-proof dish; cover and bake at 300*F for 15 minutes, stirring occasionally and adding a small amount of water if dish appears too dry.

Serves 6-8