Directions

1. Thinly slice scallions, and add to bowl along with corn. Add 1 tablespoon oil, and season with salt and pepper; toss to combine. Cover and refrigerate.
2. Halve jalapeno (remove ribs and seeds for less heat, if desired), and mince. Halve tomatoes. Combine in an airtight container; cover and refrigerate.
3. Coarsely grate cheese on a box grater; place into a resealable plastic bag, and refrigerate.
4. Preheat oven to 475 degrees. Arrange tortillas on two baking sheets; brush both sides with remaining 2 tablespoons oil. Rinse and drain beans; sprinkle over tortillas. Top with tomatoes, jalapeno, and cheese. Bake until golden and crisp, about 10 minutes, rotating sheets halfway through.
5. While tostadas are baking, pit and peel avocado; dice. Toss with corn mixture to combine.
6. To serve, top tostadas with corn relish, and, if desired, sour cream.