1. Preheat the oven to 400 F; Spray a 13-by-9-inch baking pan with cooking oil spray; Set aside.

2. Stack the tortillas on a cutting board, and slice through them lengthwise into 3 strips each (The strips will not be uniform because of their circular shape; This is OK) Set aside.

3. Pour the corn and black beans into a colander, and rinse with warm tap water to begin defrosting the corn and rinse the beans; Set aside to drain.

4. Brown the ground beef in a large skillet, when it has just lost its pink color, add the onion, chili powder, and cumin to the skillet and cook until the onions are soft and translucent.

5. Add the minced garlic and cook for about 30 seconds til one minute stirring constantly.

6. Add the tomatoes and their juice, the tomato sauce, and sugar; cook until warmed through. Spoon enough sauce into the bottom of the dish to cover it; Cover the sauce with a layer of corn tortillas (it's fine if they overlap somewhat).

7. Break the egg into a medium-size mixing bowl, and beat with a whisk or fork until foamy; Add the sour cream and 2 cups of the cheese; Stir to mix well; Spoon half of the sour cream mixture evenly over the tortilla layer and spread it out with the back of a spoon; Spoon a thin layer of meat and sauce over the cheese mixture; Scatter half of the corn and black beans over meat mixture.

8 . Place another layer of tortillas; Top with the remaining sour cream mixture, the remaining black beans and corn, and half of the remaining meat mixture; Place the remaining tortilla strips over the dish; Pour the remaining meat sauce mixture over the tortillas, and spread it evenly with the back of a spoon to moisten all of the tortilla strips.

9. Cover the dish with foil, and bake for 30 minutes, or until hot and bubbly.

10. While the dish bakes, rinse and trim the green onions; Slice the green onions thinly; Set aside.

11. If using the black olives, drain them well, and set aside.

12. After baking lasagna, scatter the green onions and olives, if using, evenly over the dish; Return the dish to the oven, uncovered, for 5 more minutes.

13. Remove the dish from the oven, and scatter the remaining cup of Mexican cheese evenly over the dish.

14. Return the dish, uncovered, to the oven, and bake until the cheese melts, about 3 minutes.

15. Remove the lasagna from the oven, and let it stand 10 minutes; Slice into squares and serve.