Slice the zucchini into 1/2-inch-thick slices. Place on a large plate and sprinkle with the salt. Let stand at room temperature for 30 minutes.
Preheat oven to 450 degrees F. Line a rimmed baking sheet with foil and spray it with olive oil spray.
Rinse the zucchini slices in a colander and pat dry with paper towels. Spread on the prepared baking sheet. Lightly spray with olive oil spray. Bake 10 minutes on each side, until tender and lightly browned.
Spoon a little marinara sauce on top of each zucchini slice. Top with cheese and pepperoni. Return to the hot oven for 2 minutes or so, just until cheese is melted. Serve immediately.