Preheat your oven to 375°F (190°C).
Slice the tops off the tomatoes and use a spoon to hollow out the insides, leaving a sturdy shell. Dice the scooped tomato flesh and set aside.
In a medium saucepan, combine the quinoa and vegetable broth. Bring to a boil, then reduce heat to low, cover, and simmer for 15 minutes or until the quinoa is cooked and the liquid is absorbed.
While the quinoa is cooking, heat the olive oil in a skillet over medium heat. Add the red onion and garlic, cooking until softened, about 3 minutes.
Stir in the black beans, reserved diced tomato flesh, cumin, smoked paprika, salt, and pepper. Cook for another 5 minutes until the mixture is heated through.
Remove the skillet from heat and gently fold in the cooked quinoa and chopped parsley.
Spoon the quinoa and black bean mixture into each tomato shell. Place the stuffed tomatoes in a baking dish.
Sprinkle the tops with crumbled feta cheese.
Bake in the preheated oven for 10 minutes, or until the tomatoes are tender and the cheese is slightly golden.
Garnish with fresh basil leaves before serving, if desired.