Meanwhile, heat oil in a 12-inch cast-iron skillet over high heat. Add turkey; cook, stirring to crumble until lightly browned, 4 to 5 minutes. Add cauliflower, bell peppers, onions, carrots, and garlic; cook, stirring often, until the vegetables are softened, 5 to 7 minutes. Add tomato sauce, brown sugar, Worcestershire, mustard, salt and pepper. Bring to a boil over medium-high heat. Reduce heat to medium; simmer, stirring occasionally, for 2 minutes.