Preheat your oven to 200°C (390°F) and line a baking sheet with parchment paper.
Slice the tops off each bell pepper and carefully remove the seeds and membranes to create a hollow cavity. Place the peppers cut-side up on the prepared baking sheet.
In a mixing bowl, combine the cooked quinoa, drained black beans, diced tomatoes, minced garlic, and chopped herbs. Mix gently until well incorporated.
Season the filling with cumin, smoked paprika, salt, and pepper, adjusting to taste. Stir again to evenly distribute the spices.
Using a spoon, generously stuff each hollowed-out pepper with the quinoa mixture, pressing lightly to pack the filling inside.
Brush the outside of each stuffed pepper with olive oil, giving them a shiny, slightly blistered appearance as they roast.
Roast the peppers in the oven for about 25-30 minutes until the skins blister and the peppers are tender when pierced with a fork.
While the peppers are roasting, simmer additional diced tomatoes with garlic and herbs in a saucepan for 10 minutes to make a simple tomato sauce.
Remove the peppers from the oven and let them rest for 5 minutes. Drizzle with the warm tomato sauce and garnish with fresh herbs.
Serve the peppers warm, enjoying the vibrant colors, smoky aroma, and satisfying texture of the hearty filling.
