Bring the quinoa and water to the boil in a saucepan over high heat. Reduce heat to medium-low, cover and simmer until the quinoa is tender, 20 to 25 minutes.
Preheat oven to 180 C / Gas 4. Lightly grease a small baking dish. Halve the red peppers lengthways. Remove the seeds and ribs but leave the stem intact so the pepper bowls hold their shape; place cut-side-up into the prepared baking dish.
Toss the chopped apple with the lime juice, olive oil, garlic, parsley, mint, tomatoes and spring onions. Fold in the quinoa and season to taste with salt and pepper. Fill the cut peppers with this mixture and fill the baking dish with about 5mm of water.
Bake in preheated oven until the peppers are tender and the quinoa is hot, about 20 minutes.
Very tasty. Will be amking it again but perhaps reducing the quantity of stuffing slightly - I had a lot left over and so have put it in the freezer. If it freezes well that will be another bonus! - 30 Mar 2014