Preheat the oven to 350 °.

Cut the peppers in half lengthwise and remove their cores and ribs. Place them cut side up into a 9-by-13 inch baking dish. Cover the dish with aluminum foil; bake for 20 minutes, until the peppers are slightly softened, then remove from the oven, uncover and let cool slightly.

Meanwhile, combine the tomatoes, spinach, onion, quinoa, egg, the 2 tablespoons of parsley, thyme, 1⁄2 teaspoon of salt and 1⁄4 teaspoon of the pepper in a mixing bowl until incorporated. Add the turkey and mix with your hands until just combined.

Stir together the reserved juice from the tomatoes, the tomato sauce,the remaining 1⁄4 teaspoon of salt and the remaining 1⁄4 teaspoon of pepper in a medium bowl to form a thick sauce.

Fill the pepper halves with the turkey-quinoa mixture, then spoon some of the tomato sauce mixture over the peppers; pour the rest on the bottom of the dish.

Cover tightly with aluminum foil and bake for 30 minutes, then uncover and bake for 25 to 35 minutes, until the filling reaches an internal temperature of 165 degrees on an instant read thermometer.

Serve with some of the sauce (from the baking dish) spooned on top. Garnish with a little extra parsley.

Make ahead: Assembled, unbaked peppers can be covered and refrigerated up to 2 days in advance.