Adjust racks to top and middle positions and preheat oven to 425 degrees. Wash and dry produce.

Halve, peel, and thinly slice half the onion (whole onion for 4 servings). Thinly slice jalapeño into rounds, removing ribs and seeds for less heat. Cut potatoes into ½-inch-thick wedges; halve wedges crosswise. Zest and quarter lime. Trim and thinly slice scallions on a diagonal.

In a small microwave-safe bowl, combine sliced onion, vinegar, 1 TBSP sugar (2 TBSP for 4 servings), a small pinch of salt, and as much jalapeño as you like. Cover with plastic wrap and microwave until onion is softened, 30-60 seconds.

Remove plastic wrap and set aside to pickle, stirring occasionally.

In a large bowl, toss potatoes with a large drizzle of oil, half the garlic powder (you'll use the rest in the next step), salt, and pepper.

Divide potatoes between two baking sheets in a single layer; roast on top and middle racks, swapping rack positions halfway through, until browned and tender, 20-25 minutes. (For 4 servings, work in batches, reheating the first batch once the second batch is done.)

While potatoes roast, in a second small bowl, combine ketchup with half the mayonnaise. If necessary, add water 1 tsp at a time until mixture reaches a drizzling consistency.

In a third small bowl, combine half the mustard (all for 4 servings), remaining mayonnaise, and remaining garlic powder until thoroughly combined. Add juice from one lime wedge (two wedges for 4) and as much lime zest as you like. If necessary, add water 1 tsp at a time until mixture reaches a drizzling consistency.

Cut hot dogs on a diagonal into ½-inch-thick pieces.

Heat a drizzle of oil in a large pan over medium-high heat. Add hot dogs and cook, stirring occasionally, until pieces are browned on at least one side, 1-2 minutes.

Divide potatoes between plates; top with hot dogs. Drizzle with lime aioli and salsa rosada; top with pickled onion and jalapeño (draining first). Garnish with crispy fried onions and scallions. Serve.