Adjust rack to top position and preheat oven to 450 degrees. Wash and dry produce.

Slice potatoes into ½-inch-thick wedges. Toss on a baking sheet with a drizzle of oil, salt, and pepper. Roast on top rack until lightly browned and tender, 20-25 minutes.

Meanwhile, peel and slice onion into ¼-inch-thick rounds, keeping layers intact. Halve buns.

In a small bowl, combine jam, chili powder, BBQ sauce, and 2 tsp water (4 tsp for 4 servings). Season with salt and pepper.

Heat a drizzle of oil in a large pan over medium-high heat. Add onion rounds and cook until tender and browned at the edges, 3-5 minutes per side. Season with salt and pepper. Transfer to a plate.

Meanwhile, in a large bowl, combine beef*, salt, and pepper. Form into two patties (four patties for 4 servings), each slightly wider than a burger bun. 

Once onion rounds are done, heat a drizzle of oil in same pan over medium-high heat. Add patties and cook to desired doneness, 3-5 minutes per side.

While patties cook, toast buns until golden brown. Evenly spread cut sides with half the ancho BBQ sauce (you’ll use the rest in the next step).

Add mayonnaise to bowl with remaining ancho BBQ sauce; stir to combine. 

Fill buns with patties and griddled onion. Divide burgers and potato wedges between plates. Serve BBQ mayo on the side for dipping.