To make the mango salsa: In a bowl, combine the mango, onion, jalapeno pepper, cilantro, lime zest and juice, tequila and salt. Toss well. Let sit at room temperature for 20 minutes before serving.
To make the barbecue salmon: preheat the boiler to high and set the oven rack about 6" below it. In a bowl, whisk together the sugar, paprika, onion powder, garlic powder, chili powder, salt and pepper. Rub the mixture all over the salmon fillet. Brush with the barbecue sauce.
Broil the salmon for 6 to 8 minutes, or until just opaque and flaky.
To make the lime butter: In a bowl, stir together the butter, lime zest, and salt until combined. While the salmon is still hot, pat the lime butter over top and let it melt. Top with the mango salsa and serve.