Sauté onion in oil and add cinnamon, chili powder and cumin. Stir in enchilada
sauce and diced tomatoes. Set aside 1 cup sauce. Add to remaining sauce the corn,
olives, green chiles, shrimp or crabmeat and 1 cup cheese.
In a 3-quart shallow casserole dish, cover bottom with some of the tortillas.
Spread 1/3 of shrimp/crabmeat mixture over tortillas; repeat with 2 more layers.
Top with remaining tortillas, sauce and cheese.