1. For the Butter: In a small bowl, mix the butter, lime juice, lime zest, salt and pepper.
2. Place the bowl in the refrigerator to cool.
3. For the Salsa: In a large bowl, mix together mangoes, onion, peppers, tomatoes, cilantro, lime juice, salt and pepper until combined.
4. Place the bowl in the refrigerator to cool.
5. For the Fish and Corn: Place the ears of corn directly on a hot grill (450° to 550°).
6. Cook on all sides for 10 to 12 minutes.
7. On a plate, combine olive oil and blackened seasoning and thoroughly coat the mahi mahi on all sides.
8. Once coated, place the fish on a hot grill and cook for 4 to 5 minutes on each side or until there are dark grill marks and the fish is cooked through.
9. Once cooked remove the fish and the corn from the grill.
10. Shuck the corn and cut the cob into 3 inch thick slices.
11. On one side of the plate lay down a small amount of mango salsa and place the fish right on top.
12. On the other side of the plate stack the corn slices as high as you can and top off with a small amount of lime butter.