Preheat oven to 400F.
Meanwhile in a bowl combine the lime juice, garlic, mustard, mayonnaise, and olive oil. Stir and add more oil if too pungent. Season to taste. (This dressing can store well in the refrigerator for up to a week)
Place the cauliflower florets in a bowl and add the mustard lime dressing to your liking. Add the fresh tarragon and serve.
Serve either warm or at room temperature.