In a bowl, toss together the salmon,¼ cup grated onion, cumin, paprika,1 tablespoon lime juice and mayonnaise.
Season with salt and pepper and toss to combine. Set aside.
Cut the avocados in half, remove the pits, and scoop the flesh out of their shells into a small bowl.
Add the lime juice, hot sauce, remaining onion, garlic, salt, and pepper and toss well. Mix well and taste for salt and pepper.
To assemble: Place the arepas on a platter and top them with the salmon.
Add avocado mixture on top of the salmon. Season with salt and pepper, to taste. Add fresh cilantro on top and serve.