Heat the broiler, if using to char the bell peppers.

• Peel and coarsely chop the onion.
• Cut a small corner from the ground turkey packaging and drain off any excess liquid. Transfer to a plate; pat dry with a paper towel.
• Rinse the black beans.

In a large frying pan over medium-high heat, warm 1 to 2 tablespoons oil until hot but not smoking. Stir in the onion, season with salt and pepper, and cook until starting to soften, 1 to 2 minutes. Stir in the Southwestern spice blend and cook until fragrant, about 1 minute.
Add the turkey, season with salt and pepper, and cook, stirring to break up the meat, until lightly browned but not yet cooked through, 3 to 4 minutes. Add the beans and tomatoes and cook, stirring occasionally, until the turkey is cooked through and the beans are warm, 2 to 3 minutes. Remove from the heat and season to taste with salt and pepper.
While the filling cooks, prepare the peppers.

• Coarsely chop the cilantro.

On the stovetop directly over a flame, or on a sheet pan under the broiler, roast the bell peppers, turning frequently, until blistered and charred all over, 5 to 7 minutes. Transfer to a cutting board to cool slightly. Scrape off the charred skin, if desired; cut the peppers in half lengthwise and remove the ribs and seeds. Stuff the peppers with the turkey-bean filling. While the peppers roast, prepare the cilantro.

Transfer the chiles rellenos to individual plates, drizzle with as much “queso” as you like, and garnish with the cilantro. Serve any remaining “queso” on the side.