Preheat your oven to 375 degrees F and spray a 9-inch deep-dish pie pan with nonstick spray. Set aside.
Take 9 of your 10 corn tortillas and cut them into wedges. The wedges should be about 4 inches wide at the widest part (the circular edge) and then come to a point on the other side. Save the scraps.
Place the wedges in the microwave (including the 10th tortilla that you did not cut into a wedge) for about 10 seconds to warm them up and loosen them so they bend without cracking. You may need to do this in batches.
Strategically place the wedges in the pie pan, by having the widest part of the wedge line the edges of the pan. Each wedge point should meet in the middle of the pan. It is OK if they overlap. Place the whole corn tortilla in the center, on top of the others.
Heat the canola oil in a large nonstick skillet over medium heat. Add the onion and cook until tender, about 6 minutes. Stir in the cooked chicken, chili powder, garlic powder, cumin, paprika, and cayenne pepper. Season with salt and black pepper. Cook for 1 minute, or until the spices become aromatic. Stir in the salsa and cook for an additional minute, then remove the pan from heat.
In a small bowl, combine the ricotta cheese, cheddar cheese, and Monterey jack cheese until incorporated. Season the cheese mixture with salt and black pepper.
To assemble the tex-mex pie, spoon half of the chicken mixture into the pie dish, directly on top of the corn tortillas. Cover the chicken mixture with a single layer of tortilla scraps (use about half of them). Top the corn tortilla scraps with the corn and diced green chilies. Dollop half of the ricotta cheese mixture haphazardly on top. Cover the cheese with another layer of tortilla scraps (using what is left) and then top the scraps with the remaining chicken mixture. Dollop the remaining cheese on top.
Cover the pie dish with foil and bake for 50 minutes. After 50 minutes, remove the foil and bake for an additional 10 minutes. Remove from heat and let stand for 10 minutes before serving. Garnish with fresh cilantro and green onions and enjoy immediately!