Squeeze half of a lime into a bowl and add the salt. Toss the sweet potatoes in the lime-salt mixture.
Wrap each potato individually in aluminum foil, and bake for 45 minutes-1 hour, or until soft (alternatively, you could cook them in the microwave for about 10-15 minutes, but NOT with the aluminum foil)
While the sweet potatoes are baking, prepare the filling.
In a pan, heat the olive and add the onions, salt, and pepper. Cook until starting to turn translucent.
Add the red pepper and cook until the onions and peppers are soft.
Add the garlic and cook for another minute. Add the black beans, juice of a lime, chili powder, cumin, and water, and simmer for 8-10 minutes, or until heated through. You can keep covered over a low heat until the sweet potatoes are ready.
Stir the pineapple and cilantro into the black bean mixture
Slice open the baked sweet potatoes, and fill with the black bean mixture. Top with the desired garnishes.