1In 3-quart Dutch oven, place rutabagas, carrots and enough water to cover; add 1/2 teaspoon of the salt. Heat to boiling; reduce heat to low. Cover; simmer 30 to 35 minutes or until tender. Drain.
2Meanwhile, in 12-inch nonstick skillet, melt 1/4 cup of the butter over medium heat. Cook onion in butter 25 minutes, stirring occasionally, until very tender.
3In large bowl, mash rutabagas and carrots until almost no lumps remain. Add onion, whipping cream, pepper, remaining 1/4 cup butter and remaining 1/2 teaspoon salt; stir until well blended. Sprinkle with bacon. Garnish with rosemary.