Prep and Combine: Carefully wash and pat dry the lettuce leaves, setting them aside. In a small bowl, whisk together all the spices: cumin, ancho chili powder, smoked paprika, granulated garlic, Mexican oregano, and the optional cayenne.
Sauté the Base: Heat the olive oil in a large Dutch oven over medium heat. Add the diced onion and bell pepper and cook until they begin to soften, about 4-5 minutes. Stir in the tomato paste and the spice blend, cooking for one minute more until fragrant.
Brown the Turkey: Add the ground turkey to the pot. Use a spatula to break the meat into fine crumbles as it cooks. Continue cooking for 6-8 minutes, until the turkey is no longer pink.
Simmer the Sauce: Pour in the no-salt-added chicken broth, stirring to combine and scraping any browned bits from the bottom of the pot. Bring the mixture to a simmer.
Reduce and Thicken: Lower the heat to maintain a gentle, steady simmer. Let the filling cook, uncovered, for 20-25 minutes, stirring occasionally. The sauce is ready when it has reduced and thickened to coat the turkey crumbles.
Assemble and Serve: Spoon the warm turkey filling into the prepared lettuce leaves. Garnish generously with fresh cilantro and serve immediately with lime wedges on the side for squeezing.