Directions

1. Preheat oven to 400 degrees. Using a paring knife, trim tortillas to fit a 9-inch springform pan (use the removable bottom of the pan as a guide). Assemble pan with the bottom upside down; lightly oil bottom and sides. Set aside.
2. In a large skillet, heat oil over medium. Add onion, cumin, and red-pepper flakes; season with salt and pepper. Cook until onion has softened, 3 to 5 minutes. Stir in tomato paste. Raise heat to medium-high; add beef and garlic. Cook, breaking up meat with a spoon until no longer pink, 4 to 6 minutes. Add corn and spinach; stir until spinach has wilted, about 2 minutes.
3. Place one tortilla in the prepared pan. Spreading evenly, top with 1 1/2 packed cups beef mixture, then 1/2 cup cheese. Repeat with two more layers. Top with last tortilla, and sprinkle with remaining 1/2 cup cheese.
4. Bake pie until top is lightly browned, 15 to 20 minutes. Run knife around edge of pan; remove sides. Using two wide metal spatulas, lift pie from bottom of pan, and transfer to a cutting board. Cut into wedges. If desired, serve with cilantro and sour cream.