Heat 1 tbsp oil in a medium sized pot over medium heat, and saute the onion, bell pepper, and jalapeno until tender.
Throw in minced garlic and cook for one minute. Empty pot and set the mixture aside.
Heat 1 tbsp oil in same pot. Stir in the turkey, and cook until evenly brown. Drain.
Return both the onion/pepper mixture, and the turkey to pot and mix in tomatoes, pumpkin, and beans.
Season with chili powder, cumin,pepper, and salt, and cayenne if using.
Reduce heat to low, cover, and simmer 20 minutes.
Serve topped with shredded cheese and plain Greek yogurt.