Place oven rack in lower third of oven and preheat oven to 450 degrees.
Stir together beans, corn, salsa, tomato sauce, cheese, cilantro, scallions, and cumin in a large bowl.

Heat a 12-inch heavy skillet over high heat until smoking. Brush both sides of each tortilla with oil and fry, turning over once, until puffed and golden in spots, about 1 minute.

Put 1 tortilla in a well-oiled 15- by 10-inch shallow baking pan, then spread with 1 1/3 cups of filling. Repeat layering twice, then top with remaining tortilla, gently pressing to help layers adhere

Bake until filling is heated through, about 12 minutes. Transfer with a large metal spatula to a platter, then cut pie into wedges with a serrated knife.