Wash and dry produce. Trim, peel, and cut carrots on a diagonal into 1/2-inch-thick pieces. Halve, peel, and cut onion into 1/2-inch-thick wedges. Trim and halve zucchini lengthwise; cut crosswise into 1/2-inch-thick half-moons.

Heat a large drizzle of oil in a large pan over medium-high heat. Add carrots, onion, and zucchini; season with garlic powder, half the Italian Seasoning (all for 4 servings), salt, and pepper. Cook, stirring occasionally, until veggies are softened and lightly browned, 7-10 minutes. Add crushed tomatoes, 1/4 cup water, and 1/2 tsp sugar (1/2 cup water and 1 tsp sugar for 4). Cook, stirring occasionally, until sauce has slightly thickened, 2-4 minutes.

Meanwhile, heat a small pot over medium heat. Add polenta and 1/3 cup water (2/3 cup for 4 servings). Mash with a potato masher until mostly smooth, 30-60 seconds. Whisk in sour cream, cream cheese, Parmesan, and 1 TBSP butter (2 TBSP for 4); cook, whisking occasionally, until thickened, 3-4 minutes. Taste and season with salt and pepper if desired. (If polenta seems too thick, add water 1 TBSP at a time until it reaches desired consistency.) Meanwhile, halve and toast ciabatta.

Cut ciabatta on a diagonal into triangles and drizzle with olive oil. Divide polenta and ragù between shallow bowls in separate sections. Serve ciabatta on the side. Chicken is fully cooked when internal temperature reaches 165°.