Place all the salsa ingredients in a bowl and stir to combine well. Set aside.
For the Pickled Onions:
In a saute pan, combine the sliced onions, sugar, lime juice, and water. Bring to a boil, and stir occasionally 1-2 minutes, until the sugar has dissolved and the liquid has reduced slightly. Transfer to a mixing bowl and set aside to pickle.
For the Tacos:
In a mixing bowl, combine the rice flour, cumin, paprika, and salt. Place half of flour mixture in a shallow bowl. Pat the fish dry, and dredge on both sides with the flour.
Heat a thin layer of oil in a saute pan, add the fish and cook 3-5 minutes on each side, until cooked through and golden brown. Remove from the heat and break into pieces.
Place the remaining flour mixture in a mixing bowl and stir in 1/4 cup water. Whisk well to create a batter.
Heat a thin layer of oil in the saute pan, Dip the avocado slices into the batter and allow excess to drip off.
Cook the coated avocado in the saute pan 1-3 minutes, until crispy. Transfer to a paper towel-lined plate.
Heat the tortillas if desired, and fill with fish, avocado, pickled onions, mango pineapple salsa, and extra cilantro.