Preheat oven to 300°F with a rack in the center. Stack tortillas and wrap in foil; place on center oven rack while oven heats to warm tortillas until step 6.

2. Prep ingredients

Halve and thinly slice all of the onion. Finely chop 3 tablespoons of the onion; reserve for step 6. Cut pineapple into ¼-inch pieces. Rinse shrimp, pat very dry, and season all over with salt and pepper. Thinly slice lettuce crosswise.

3. Cook onions

Heat 1 tablespoon oil in a medium skillet over medium-high. Add sliced onions and cook, stirring occasionally, until softened and browned in spots, 6-8 minutes.

4. Cook shrimp

To skillet with onions, add shrimp, all but 2 tablespoons of the pineapple, and ½ teaspoon chipotle powder (or more depending on heat preference). Cook, stirring once or twice, until shrimp are just cooked through, about 3 minutes.

5. Finish shrimp

Reduce skillet heat to low. Add 1 tablespoons butter and1 tablespoon vinegar. Cook, scraping up any browned bits from bottom, until butter is melted. Season to taste with salt and pepper.

6. Finish & serve

Pick cilantro leaves from stems; discard stems. Divide shrimp mixture and sauce among tortillas. Top with lettuce, remaining pineapple, and reserved chopped onions. Garnish with cilantro leaves and sprinkle with any remaining chipotle powder, if desired. Enjoy!