Stir water, ketchup, onion, soy sauce, Worcestershire sauce, olive oil, honey, flour, garlic powder, black pepper, and poultry seasoning together in an oven-safe Dutch oven. Simmer over medium heat, stirring occasionally, until flavors blend, about 5 minutes. Cool for 10 minutes.

Preheat the oven to 375 degrees F (190 degrees C).

Place chicken in the Dutch oven and turn to coat with ketchup mixture. Spoon 1/4 of the mixture, including onions, into the chicken cavity. Place chicken breast-side down; cover with an oven-proof lid.

Bake chicken in the preheated oven, basting once, for 45 minutes. Uncover the Dutch oven and increase heat to 400 degrees F (200 degrees C).

Turn chicken breast-side up and bake until chicken has browned, about 15 more minutes. Let chicken stand for about 10 minutes before serving.