Quinoa: Bring 1 cup water to boil in a small saucepan then add quinoa. Cover and cook for 10 minutes, or until water is absorbed.
Filling: Meanwhile add 1 Tbsp oil to a large saucepan over medium heat. Add garlic, onions, cumin, paprika, salt, and pepper, cooking until onions begin to soften. Add drained beans and corn, as well as cooked quinoa and half of the cheese. Stir to combine.
Assemble: Cut bell peppers in half lengthwise and remove ribs and seeds. Stuff mixture into peppers and place on a parchment paper-lined baking sheet. Preheat oven to 425 degrees F (218 C).
Enchilada Sauce: In a medium saucepan, add 1 Tbsp oil, tomatoes, salt, and pepper. Cook over medium/high for 5 minutes, or until tomatoes begin to break down. Use an immersion blender (or transfer to a blender) and blitz until smooth. Spoon over peppers, sprinkle with remaining cheese, and bake for 20 minutes, or until cheese is golden and bubbly.