Adjust rack to top position (top and middle positions for 8 servings) and preheat oven to 425 degrees. Wash and dry produce. Line a baking sheet (two baking sheets for 8) with parchment paper.

Cut potatoes into ¼-inch wedges. Toss on prepared sheet with a drizzle of oil, garlic powder, salt, and pepper. Roast on top rack until browned and tender, 20-25 minutes. (For 8, divide between two prepared sheets and roast on top and middle racks, swapping rack positions halfway through.)

Heat a large dry pan over medium-high heat. Add bacon*; cook, turning occasionally and adjusting heat if browning too quickly, until crispy, 6-10 minutes. Turn off heat; transfer to a paper-towel-lined plate. Once cool enough to handle, roughly chop.

Discard all but a thin layer of bacon fat from pan.

Meanwhile, halve, peel, and thinly slice half the onion (whole onion for 8 servings). Trim and thinly slice scallions, separating whites from greens. Mince whites. Finely dice tomato. Quarter lime. Finely chop cilantro.

In a medium microwave-safe bowl, combine sliced onion, vinegar, 1 tsp sugar, and 1 tsp salt (2 tsp sugar and 2 tsp salt for 8). Cover tightly with plastic wrap and microwave until sugar is dissolved and onion is bright pink, 30-60 seconds.

Carefully uncover and set aside, stirring occasionally, until ready to serve.

In a small bowl, mix together scallion whites, tomato, juice from two lime wedges (four wedges for 8), and a pinch of salt and pepper.

Heat pan with reserved bacon fat over medium heat (add a drizzle of oil if pan seems dry). Add beef*, Mexican Spice Blend, stock concentrate, salt, and pepper. Cook, breaking up meat into pieces, until cooked through, 4-6 minutes.

Stir in beans and their liquid and tomato paste. Reduce heat to medium low. Bring to a simmer, then cook, stirring occasionally, until slightly thickened, 2-3 minutes more. Remove from heat. Taste and season with salt and pepper.

Once potato wedges have roasted 20-25 minutes, remove baking sheet from oven; heat broiler to high.

Carefully sprinkle potato wedges with one packet of Mexican cheese blend (two packets for 8 servings). Evenly spread chili over top. Sprinkle with remaining Mexican cheese blend.

Broil on top rack until cheese is melted and bubbling, 2-3 minutes.

Top potato nachos with bacon, pico de gallo, guacamole, cilantro, scallion greens, and as much pickled onion (draining first) as you like. 

Drizzle with sour cream and serve family style. TIP: If you like things spicy, serve with your favorite hot sauce!