Preheat oven to 350 degrees F. Line a 9x13 baking dish with parchment paper.
In a large bowl, combine lemon juice and cooked quinoa. Add tuna, feta, onion, olives, tomatoes, parsley, pine nuts, and golden raisins. Toss well to mix. Add olive oil and salt, to taste. Mix well.
Spoon the filling into each bell pepper cavity. Place on prepared baking dish, cavity side up, and bake until the peppers are tender and the filling is heated through, about 25-30 minutes.