Add rutabaga and salt to a large pot of boiling water. Simmer for 25 minutes until rutabaga is fork tender and soft. Drain, reserving 2 tablespoons cooking liquid.
Add to a high speed blender or food processor, with butter, cooking water, and cream. Blend for 30-40 seconds, scraping down sides halfway through, and blend until as smooth or as chunky as you’d like.
For tomatoes, heat olive oil to medium in a sauté pan. Once warm, add garlic, stirring to sauté, for 1 minute. Then add tomatoes, parsley, and salt. Cook on low, barely seeing bubbles coming to the surface, for 30 minutes. Add to warm rutabaga and serve with fresh herbs if you desire.
If you're avoiding dairy, you can substitute more cooking water in place of the butter, and unsweetened, plain nut milk for the cream. But if you can have it, do it. It's so incredibly good.