Heat the oil in a large saucepan or dutch oven over medium heat. Once hot and shimmering, add the onion and celery and sprinkle with salt and pepper. Sauté until tender, about 4 minutes.
Add the garlic, Italian seasoning, and red pepper flakes and cook until fragrant, about 1 minute more.
Add the turkey and cook 7 minutes, stirring frequently, until mostly cooked through. Stir in the wine and continue to cook until evaporated by about one-third.
Stir in the marinara sauce and diced tomatoes. Simmer another 15 minutes, to allow the flavors to meld.
Serve over cauliflower rice or your favorite keto noodles.
