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.