Preheat the oven to 350°F (180°C), or 160°C if using a fan oven.
Prepare all of the red bell peppers by slicing them in halves, removing the seeds and the membrane.
Brush them with 1 tablespoon of olive oil inside and out, and roast them in the preheated oven until they're just undercooked, about 10-15 minutes.
Meanwhile, heat the remaining 1 tablespoon of olive oil in a large skillet over medium heat. Add the onion and cook, stirring occasionally, until just softened, about 4 minutes. Add the minced garlic to the skillet and cook for another minute, until fragrant.
Stir in the rice, then pour in the vegetable stock. Stir in the diced tomatoes along with their liquid and the taco seasoning, and add a pinch of salt. Allow it to cook covered over low heat for about 15 minutes, or until the rice is fully cooked. Make sure to stir every few minutes as the rice can stick to the bottom.
Add the drained black beans and corn to the skillet, stirring until everything is fully combined and warmed through. Taste the filling and adjust seasonings to your preference.
Take the roasted peppers out of the oven, do not switch the oven off.
Generously fill the roasted bell pepper halves with the rice mixture, distributing evenly, and then sprinkle the tops with cheese.
Bake, uncovered, in the oven until the cheese is bubbling for about 5 minutes.
To serve, garnish the stuffed peppers with fresh cilantro and accompany with lime wedges, if desired.