Steak Tostadas with Cilantro Sour Cream

Preheat oven to 475 degrees. Line a large rimmed baking sheet with aluminum foil. Place tortillas on sheet (it's fine if they overlap); sprinkle with cheese. Bake until edges are golden, 4 to 6 minutes.

Meanwhile, in a large bowl, toss together steak, mushrooms, corn, and scallions; season with salt and pepper. Top tortillas with steak mixture. Bake until warmed through, 6 to 8 minutes.

Meanwhile, in a small bowl, stir together sour cream, cilantro, and lime juice; season with salt and pepper. Serve tostadas topped with cilantro sour cream and garnished with cilantro and lime wedges.