Char the skins of the chiles over a gas burner, grill or under the broiler. Put the chiles in a plastic bag or some other closed container to steam for 20 minutes. Scrape off the skins, remove the seeds and stems, and cut into strips or dice them. Salt well and soak in the 1/4 cup lime juice.
When you are ready, flake out the smoked salmon; discard any skin and bones. Heat your tortillas and load them up with the salmon, the strips of roasted pepper, and avocados. Top with the crema, pumpkin seeds, and, if you want, lime juice and hot sauce.
Notes
If you don't have any smoked salmon, you can use any smoked fish here. Smoked bluefish or mackerel are great choices, as are smoked trout, mullet or amberjack. And of course, smoked marlin is the classic in Mexico.