Pound the turkey cutlets 1/4 inch thick and season with salt and pepper. Spoon 1 tablespoon cheese in the center of each cutlet and top with the spinach. Fold the cutlets in half and close with a toothpick.
In a large skillet, heat the olive oil over medium-high heat. Add the cutlets and cook until browned, about 2 minutes per side. Add the tomatoes with their juice and the fennel seeds; bring to a boil. Lower the heat, cover and simmer until the turkey is cooked through, about 10 minutes.