In a 2- or 3-quart saucepan, heat the olive oil and sauté the onion and ground turkey over medium heat for about 10 minutes. Add the barley and sauté, stirring often, for a few minutes. Add the water, bring to a boil, reduce the heat, and simmer for 45 minutes or until all the water is absorbed.
Bring a large pot of water to a boil. Meanwhile, cut off the tops of the peppers with care – they will be used later. Gently remove the cores and seeds to create an empty cavity. Blanch the peppers in the boiling water for 5 minutes. Remove from the water and place upside down on paper towels to drain.
Roast the sunflower seeds on a baking sheet in the preheated oven for about 5 minutes, shaking the pan often. Remove and set aside, leaving the oven on for the peppers.
When the barley is done, toss it with the sunflower seeds, cheese, herbs, lemon juice, wine, cinnamon, salt, and pepper in a large bowl. Mix well and adjust the seasonings to taste. Stuff the peppers with the mixture, put the tops back on, and place the peppers in a baking dish just large enough to hold them upright. Bake for 25 to 30 minutes, or until the barley mixture is heated through. Serve immediately.