Preheat the oven to 425°F (220ºC). Arrange tortillas on a sheet pan. Bake until lightly browned, 2–4 minutes. Remove pan from the oven.
Carefully flip tortillas. Spread ¼ cup marinara over each tortilla and sprinkle with crushed pepper over each. Arrange 1 cup spinach on each tortilla and sprinkle ⅓ cup mozzarella over each.
Bake until cheese is melted and bubbly, about 5–7 minutes.
