Before starting, preheat the oven to 450˚F. Wash and dry all produce. Core, then cut apple into 1/4-inch slices. Thinly slice green onion. Peel, then cut onion into 1/2-inch slices. Add vinegar, 1 tbsp oil and 1/4 tsp sugar (dbl both for 4 ppl) to a large bowl. Season with salt and pepper, then whisk until sugar dissolves. Add apples to dressing, then toss to combine. Set aside.

Heat a large non-stick pan over medium-high heat. When hot, add 1/2 tbsp oil (dbl for 4 ppl), then beef. Cook, breaking up beef into smaller pieces, until no pink remains, 4-5 min.** Carefully drain and discard excess fat. Add half the BBQ sauce to beef. Cook, stirring occasionally, until fragrant, 30 sec. Season with salt and pepper. Remove from heat. Transfer beef to a plate, then cover to keep warm. Carefully wipe the pan clean.

Reheat the same pan over medium-high. When hot, add 1/2 tbsp oil (dbl for 4 ppl), then onions. Cook, stirring occasionally, until tender, 3-4 min. Season with salt and pepper. Remove from heat. Transfer onions to the plate with beef, then cover to keep warm.

Meanwhile, arrange flatbreads on a parchment-lined baking sheet. (NOTE: For 4 ppl, use 2 parchment-lined baking sheets.) Toast flatbreads in the middle of the oven until softened, 2-3 min. (NOTE: For 4 ppl, toast in the top and middle of the oven, rotating sheets halfway through.)

Spread marinara sauce over toasted flatbreads. Top with beef and onions, then sprinkle cheese over top. Bake in the middle of the oven until cheese is melted and flatbreads are golden-brown and crisp, 6-8 min. (NOTE: For 4 ppl, bake flatbreads in the top and middle of the oven, rotating sheets halfway through.)

Add spring mix to the bowl with marinated apples. Toss to combine. Cut flatbread pizzas into slices, then drizzle remaining BBQ sauce over top. Sprinkle green onions over pizzas. Divide pizzas and salad between plates.