Step 1: Prepare the Bell Peppers

1. Preheat Oven to 375°F (190°C): Start by preheating your oven to the correct temperature. This ensures the peppers cook evenly and the cheese (if using) melts beautifully.
2. Wash and Prepare the Peppers: Rinse the bell peppers thoroughly under cold water. Using a sharp knife, carefully slice off the tops of the bell peppers, about ½ inch from the stem. Set the tops aside – you can chop them and add them to the filling if desired, or discard them.
3. Remove Seeds and Membranes: Using a spoon or your fingers, carefully remove the seeds and white membranes from inside each bell pepper. Ensure you remove all seeds for a smoother texture.
4. Blanch the Peppers (Optional but Recommended): Blanching the peppers slightly softens them and makes them easier to stuff and eat. Bring a large pot of salted water to a boil. Carefully place the hollowed bell peppers into the boiling water and blanch for 3-5 minutes. Remove them with tongs or a slotted spoon and immediately plunge them into a bowl of ice water to stop the cooking process. Drain well and pat dry with paper towels. If you prefer a crisper pepper, you can skip blanching, but the baking time might need to be slightly increased.
5. Pre-bake Peppers (Optional but Recommended for Softer Peppers): For even softer peppers, you can pre-bake them. Brush the inside of the peppers with a little olive oil. Place the peppers cut-side up in a baking dish and bake for 15 minutes. This pre-baking step will help them soften further before stuffing.

Step 2: Prepare the Vegetarian Filling

1. Sauté Aromatics: Heat 1 tablespoon of olive oil in a large skillet over medium heat. Add the diced onion and cook until softened, about 5-7 minutes. Add the minced garlic and diced red bell pepper (if using) and cook for another 2-3 minutes until fragrant and slightly softened. Be careful not to burn the garlic.
2. Add Spices and Tomatoes: Stir in the chili powder, cumin, smoked paprika, and dried oregano. Cook for 1 minute more, stirring constantly, until the spices are fragrant. This blooming of the spices enhances their flavor. Add the undrained diced tomatoes to the skillet and stir to combine.
3. Incorporate Rice, Beans, Corn, and Broth: Add the cooked rice, rinsed and drained black beans, and frozen corn kernels to the skillet. Pour in the vegetable broth and stir everything together well.
4. Simmer and Thicken: Bring the mixture to a simmer and cook for 5-7 minutes, stirring occasionally, until the filling has thickened slightly and the flavors have melded together. Taste and season with salt and black pepper to your liking. Adjust spices as needed – add more chili powder for heat, cumin for earthiness, or paprika for smokiness. If the filling seems too dry, add a little more vegetable broth or water, one tablespoon at a time. If it is too wet, cook for a few more minutes to allow excess liquid to evaporate.

Step 3: Stuff and Bake the Peppers

1. Stuff the Peppers: Remove the skillet from the heat. Spoon the vegetarian filling generously into each prepared bell pepper, packing it in firmly but not too tightly. Fill each pepper to the top.
2. Add Cheese (Optional): If using cheese, sprinkle shredded cheese evenly over the top of each stuffed pepper.
3. Bake: Arrange the stuffed peppers in a baking dish. You can add a little water or vegetable broth (about ½ cup) to the bottom of the baking dish to prevent sticking and create a bit of steam, which helps keep the peppers moist. Cover the baking dish with foil.
4. Bake Covered: Bake in the preheated oven for 20 minutes covered.
5. Bake Uncovered (Optional, for Cheese Meltdown): If using cheese, remove the foil and bake for another 10-15 minutes, or until the cheese is melted and bubbly and the peppers are tender but still slightly firm. If you skipped the cheese, bake uncovered for the last 10-15 minutes to allow the peppers to roast slightly and the filling to brown a bit on top.
6. Check for Doneness: The peppers are done when they are tender when pierced with a fork, and the filling is heated through. Baking time can vary depending on the size and thickness of the peppers and your oven.

Step 4: Serve and Garnish

1. Rest (Optional): Let the stuffed peppers rest for a few minutes after removing them from the oven. This allows the flavors to settle and makes them easier to handle.
2. Garnish and Serve: Serve the vegetarian stuffed peppers hot. Garnish with fresh cilantro, a dollop of sour cream or Greek yogurt, diced avocado, or salsa, if desired. See the “How to Serve” section below for more serving suggestions.