Preheat your oven to 375°F (190°C) and lightly oil a baking dish.
Wash the peppers, then carefully halve each lengthwise and remove the seeds and membranes. Arrange them cut side up in the baking dish.
In a skillet over medium heat, warm a tablespoon of olive oil. Add diced onion and sauté until fragrant and translucent, about 5 minutes. Stir in minced garlic and cook for another 30 seconds until aromatic.
Add cooked quinoa, drained black beans, diced tomatoes, smoked paprika, cumin, and a pinch of salt to the skillet. Mix well and cook for 3-4 minutes until heated through and flavors meld. Remove from heat and stir in lemon juice and chopped herbs.
Use a spoon to generously stuff each pepper half with the flavorful quinoa and bean mixture, pressing slightly to pack the filling in.
Place the filled peppers in the prepared baking dish and cover tightly with foil. Bake for 30 minutes, or until the peppers are tender and slightly blistered at the edges.
Remove the foil and bake uncovered for an additional 5 minutes to allow the tops to get a slight golden crust. Garnish with chopped parsley and cilantro before serving.
Let the peppers rest for about 5 minutes, then serve warm, enjoying the vibrant colors and savory aroma.