Preheat oven to 400 F. Line a baking sheet with parchment paper and have more parchment paper and aluminum foil handy.

Mix a marinade - in a bowl first whisk the brown sugar and salt in lime juice until completely dissolved. Add the minced garlic, curry powder, onion powder and olive oil and mix together. Reserve 1.5 to 2 tbsp of the marinade for later.

Peel the rutabaga heads and cut crosswise into 'steaks', about 1 inch thick each. Coat each steak in marinade and arrange onto the prepared baking sheet. Cover with another parchment paper sheet, then tightly cover with aluminum foil.

Roast for 1 hour. Remove the foil and top parchment paper, brush the steaks with a bit of the reserved marinade and then broil for a couple of minutes, until nicely golden and crispy on top. Watch the steaks closely during this step.

Combine the rest of the reserved marinade with the sour cream to make a dip. Serve immediately.