Pre-heat the oven to 400° F.

Slice the bolillos lengthwise down the middle and place two overlapping slices of cheese against the top side.

Heat a non-stick pan to medium or medium-high.

Add 1 tablespoon of the olive oil and half of the onions.

Toss until the onions are starting to brown.

Remove from heat before they become too soft.

Transfer to a paper plate and repeat with the rest of the sliced onions.

Then add 2-3 tablespoon of olive oil to the pan, add the shaved pastrami, and sprinkle the pinches of garlic powder and oregano.

Toss until the meat is heated, well covered in olive oil, and the seasonings are well distributed.

Add the onions and toss to mix well.

Spoon equal amounts into the prepared bolillos.

Place in the hot oven for a couple of minutes or just until the cheese finishes melting.

Serve hot.