Preheat oven to 450°F. Line a shallow baking pan with foil. Add peppers to pan. Roast, uncovered, for 10 minutes. Turn peppers. Roast about 10 minutes more or until pepper skins are evenly blackened and charred.
Set pan with peppers on a wire rack. Carefully bring edges of foil up and around peppers to fully enclose them in the foil. Let stand 15 to 20 minutes or until peppers are cool enough to handle.
Reduce oven temperature to 350°F.
Meanwhile, in a small saucepan combine broth and quinoa. Bring to boiling; reduce heat. Simmer, covered, for 12 to 15 minutes or until quinoa is just tender and liquid is absorbed. Remove from the heat.
In a large skillet cook turkey and onion over medium heat until turkey is no longer pink, stirring to break up turkey as it cooks. Drain off fat if needed. Sprinkle turkey with cumin and smoked paprika. Stir in salsa. Add cooked quinoa and, if desired, 2 tablespoons cilantro. Stir until well mixed.
Wearing clean plastic gloves,*** use a small sharp knife to carefully peel off the charred skin from the peppers. Discard skin. Use the knife to cut around the tops of the peppers to remove the stem. Cut down the length of the pepper in one place and open the pepper. Remove as many of the seeds as you can, being careful to keep the pepper intact.
Line the same baking pan with parchment paper. Lay peppers open in the prepared pan. Spoon quinoa mixture evenly into peppers. Wrap the loose edges of the peppers up around the quinoa mixture.
Bake stuffed peppers, uncovered, for 10 to 12 minutes or until heated through. Serve peppers topped with guacamole and cilantro if desired. Serve with lime wedges if desired.