Heat the oil in a small saucepan over medium high heat and add the fenugreek seeds, cumin seeds, cardamom pods and cinnamon stick. Cook 3-4 minutes stirring constantly. Add the onion and cook another minute or so. You want the onion to be slightly browned but not burned! Watch it carefully.
Add the onion mix to the slow cooker and turn it on high.
Add the tomato, turmeric and coriander to the onion mix and stir it together, letting it cook a few minutes. Stir in the squash and cook a few more minutes.
Turn the slower cooker to low, cover and cook 4 hours, stirring now and then.
Add the chilies, brown sugar, garam masala, salt, chili powder and lemon juice and stir well. Turn into a serving dish and garnish with the cilantro leaves.