Preheat your oven to 200°C (390°F). Slice the tops off the peppers and carefully scoop out the seeds and membranes, creating a hollow cavity. Lightly brush the peppers with olive oil and place them cut side up on a parchment-lined baking sheet. Roast for 15-20 minutes until they are slightly softened and fragrant, then remove from the oven and set aside.
While the peppers are roasting, heat a tablespoon of olive oil in a skillet over medium heat. Add the diced onion and cook, stirring frequently, until translucent and fragrant, about 3-4 minutes. Add the minced garlic and cook for another minute until aromatic.
Stir in the cooked grains, tomato paste, smoked paprika, and chopped parsley into the skillet. Cook for another 2 minutes, allowing the flavors to meld and the mixture to warm through. Season with salt and pepper to taste.
Once the peppers are roasted and slightly cooled, spoon the savory filling into each pepper, pressing gently to pack the mixture in. If desired, sprinkle with vegan cheese or nutritional yeast on top for a cheesy finish.
Place the stuffed peppers back in the oven and bake for an additional 10-12 minutes at 180°C (355°F), until the tops are golden and the filling is bubbling. Keep an eye on them to prevent over-browning.
Remove the peppers from the oven and let them rest for 5 minutes. This helps the juices settle and makes serving easier. Garnish with extra parsley if desired, then serve hot and enjoy the tender, smoky, and flavorful bites.