Slice the tops off the sweet peppers and set them aside for garnish if you like.
Remove and discard the seeds and membranes.
Arrange the peppers cut-side up in a 2-quart square microwave-safe baking dish, add the water to the bottom of the dish, and microwave on high for about 8 minutes, or until they just begin to soften.
While the peppers are cooking, prepare the filling.
In a medium bowl, combine the drained corn, rinsed black beans, undrained diced tomatoes, salsa, and cumin or chili powder.
Heat the pouch of brown rice according to package directions, then stir the cooked rice into the bean and corn mixture until well combined.
Carefully remove the peppers from the microwave. Generously spoon the bean and rice filling into each softened pepper. Return the dish to the microwave and cook on high for about 4 more minutes, until the peppers are tender and the filling is heated all the way through.
Serve immediately.
Don't love stuffed peppers? The filling is fantastic on its own served as a hearty dip with tortilla chips, wrapped in a warm tortilla for a quick burrito, or served over mixed greens for a taco salad.