Preheat oven to 400F.
In a medium bowl, place the two pieces of salmon; pour 1 tbsp olive oil and sprinkle salt, pepper and dried oregano.
Cut two sheets of foil. It has to be big enough to wrap the salmon and asparagus.
First place asparagus (about 8 spears) on the sheet of foil.
Layer fillets over asparagus.
Then top each with about 2 onion slices and 2 lemon slices.
Wrap sides of foil inward over salmon then fold on top and bottom of foil to enclose.
Place foil packets in a single layer on a baking sheet.
Bake in preheated oven for about 20 minutes.