Preheat the oven to 400 degrees.  Use a spoon to scoop out the middle of each zucchini half, creating “boats.”  Brush the zucchini all over with olive oil and place in a 9×13 baking dish.  Bake until the zucchini is tender, about 20 minutes.

While the zucchini is baking, cook the ground beef and onion in a skillet.  Drain the excess fat.  Return to the heat, and add the garlic.  Cook for 1 more minute.  Add the tomato sauce and spices and stir well.  In a bowl, whisk together the cornstarch and water.  Add to the meat mixture and stir.  Allow the meat mixture to come to a boil and stir while boiling for about 1-2 minutes.  Reduce the heat to low and let it simmer for 5 minutes, until it has thickened some.

When the zucchini is tender, remove it from the oven.  Spoon the meat mixture into the boats.  Top with cheese and bake for another 5-10 minutes, until the cheese has melted.  Serve topped with your favorite enchilada toppings: diced green onion, chopped tomatoes, shredded lettuce, black olives, jalapenos, sour cream, salsa, or guacamole.