Cut the top off of each pepper, reserve. Remove cores and seeds, hollowing out the peppers. Using a small, sharp paring knife, carefully carve desired Jack O'Lantern face into each pepper. Drizzle the inside of each pepper with olive oil and season generously with salt and pepper. Arrange peppers and tops in a microwave-safe 2-quart square baking dish. Pour the water around peppers.
Microwave peppers, uncovered, on 100 percent power (high) about 8 minutes or just until peppers are starting to soften.
Meanwhile, in a medium bowl stir together black beans, corn, tomatoes, rice, salsa, and cumin.
Divide bean mixture evenly among the peppers. Microwave, uncovered, on 100 percent power (high) about 4 minutes more or until filling is heated through and peppers are tender.