Zest the lemon, then cut it in half and supreme/section it. Squeeze the juice of the remaining lemon center into a small bowl.
In a medium pot on medium heat, add the onions, red chile flakes, olive oil, a nice pinch of salt and plenty of coarsely ground black pepper. Cook, stirring, until the onions are tender, 5 to 8 minutes. Add the garlic, lower the heat and stir the garlic into the onions until lost and fragrant. Add the lemon zest and juice, lemon curd, chicken stock, Worcestershire, rosemary and thyme to the pot. Bring to a simmer and cook, stirring, until thickened, another 3 to 5 minutes. Gently stir in the parsley and lemon sections. Season with salt and pepper.
Use 1/4 cup to glaze a whole chicken while grilling. Drizzle the remaining glaze over the chicken when serving.