Season: Pat dry the turkey breast with kitchen paper. Mix the curry, cinnamon, sugar, ¾ fine sea salt, and ½ teaspoon ground black pepper. Rub the turkey breast with this mixture.
Brown: Heat a little oil in the Dutch oven and brown the turkey breast on all sides, about 3 minutes per side. If the turkey breast is rather higher than flat, it will have more than only two sides to brown.
Add the chopped onions and quartered apples during the last 3 minutes of the browning time. Add the white wine and stir slightly around the turkey breast.
Braise: Place the lid on and braise the turkey on medium low heat for 1 hour, turning the breast twice in between.
Check the internal temperature after about 50 minutes if the turkey breast is relatively flat. To ensure that the turkey breast is cooked through (even a thicker one should be done after one hour), check the internal temperature using a meat thermometer. The temperature should be 74 degrees Celsius/ 165 degrees Fahrenheit.
Rest: Remove the turkey breast from the pot, cover it loosely with aluminum foil and let rest while you make the sauce.
Make the gravy: Pour the heavy cream into the pot and let bubble until slightly thickened. Adjust the taste with salt and pepper.