Preheat the oven to 350 degrees F and lightly coat a 9" x 13" casserole dish with nonstick cooking spray.
To make the enchilada sauce, place the diced tomatoes in a blender and process until smooth with no lumps, and set aside. In a large skillet, heat the vegetable oil over medium heat, then whisk in the flour and chili powder until it becomes smooth. Pour in the blended tomatoes and chicken broth along with the remaining spices, and whisk to combine. Let simmer until slightly thickened. Pour 1/2 cup of the sauce in the bottom of the casserole dish.
Meanwhile combine the chicken with the grilled corn kernels and then place a heaping 1/4 cup on each tortilla along with a decent sprinkle of cheese. Roll each tortilla up and place seam-side down in the casserole dish. Cover with the remaining sauce and the rest of the cheese and bake for 20 to 25 minutes or until melted and bubbly all over.
If you can't find the blended tortillas, regular corn tortillas will work in this recipe. Just be sure to heat them slightly before rolling so they do not break on you.From my cookbook Express Lane Cooking