For the tacos:

Whisk the salt and lime zest in just enough water to cover the shrimp when spread in a single layer; a pie plate works well. Add the shrimp, making sure they’re completely submerged, and set aside for 10-15 minutes.

Melt the butter in a sauté pan over medium-high heat. When the foaming subsides, add the bell pepper and sauté until softened and beginning to color, 3-4 minutes. Add the garlic and cook until fragrant, about 1 minute. Quickly drain the brined shrimp and add to the pan; cook, stirring, until the shrimp are just cooked through; time will depend on the size of the shrimp. Remove from the heat and stir in the cumin and red pepper flakes; taste and add salt if desired. Keep warm.

For the tortillas: Just before you start the sauté process put a cast iron skillet over medium heat; by the time you’re done with the shrimp it will be hot enough to cook the tortillas. Increase the heat to high and cook tortillas 1 at a time, flipping each once. It will take just a minute or two on each side. You’ll get some blackened spots and they’ll puff.

Set out the garnishes and let guests assemble as desired.