Arrange the pepper halves cut-side up in the cold skillet — they should fit snugly. Add 1/2 cup water, cover, and bring to a simmer over medium-high heat. Steam 6–8 minutes, until the peppers are just fork-tender but still hold their shape. Transfer to a plate and carefully wipe out the skillet.

Heat the olive oil in the same skillet over medium-high heat. Add the ground turkey, season with 1/2 teaspoon salt, and cook, breaking it into crumbles, until no pink remains, about 4–5 minutes.

Stir in the onion and cook 2 minutes. Add the garlic, Italian seasoning, remaining 1/4 teaspoon salt, and black pepper; cook 30 seconds until fragrant. Add the kale in handfuls, stirring until each batch wilts, about 2 minutes total.

Fold in the cooked rice and 1 cup of the marinara sauce. Simmer 1–2 minutes, until everything is heated through. Stir in the Parmesan and taste for seasoning.

Spoon the turkey-kale mixture generously into each pepper half and nest them back into the skillet. Pour the remaining 1/2 cup marinara around the peppers (not over the filling) and add 2 tablespoons water to the pan base.

Sprinkle the mozzarella evenly over the stuffed peppers. Cover and cook 2–3 minutes, until the cheese is melted and bubbly. Top with basil and red pepper flakes, if using, and serve right from the skillet.