1. In a medium, non-reactive bowl, drizzle the honey over the mango; stir well and refrigerate for 30 minutes to an hour. Stir in the onion, jalapenos and lime juice; cover and refrigerate for at least one additional hour, to allow the flavors to blend. Stir in the cilantro just before serving.
2. Mix all of the blackening spices together on a plate, and dredge the tuna on all sides.
3. Heat a lightly greased cast iron skillet until nearly smoking and sear the fish over high heat until desired doneness - about 15 – 30 seconds per side for rare; about 1 minute each side for medium-rare.Thinly slice and arrange the tuna on two plates; garnish each serving with about 1/4 cup of the salsa.
4. Serve immediately.Nutrition (per serving): 251 calories, 2.3g total fat, 44.2mg cholesterol, 94.5mg sodium, 943mg potassium, 30.3g carbohydrates, 5.8g fiber, 21.4g sugar, 30.4g protein.