Adjust rack to top position (top and middle positions for 4 servings) and preheat oven to 450 degrees. Wash and dry produce.

Halve, peel, and thinly slice onion. Heat a drizzle of oil in a large pan over medium heat. Add onion, ½ tsp sugar (1 tsp for 4), and salt. Cook, stirring occasionally, until tender and browned, 8-10 minutes.

In the last minute of cooking, add 1 TBSP water (2 TBSP for 4) and stir until onion is jammy. Turn off heat; transfer to a plate. Wipe out pan.

Meanwhile, halve, core, and thinly slice pear. Roughly chop walnuts.

Place flatbreads on a baking sheet and bake on top rack until lightly toasted, 5-7 minutes. (For 4 servings, divide between two baking sheets; toast on top and middle racks, swapping rack positions halfway through toasting.)

While flatbreads toast, heat a drizzle of oil in pan used for onion over medium-high heat. Add pear and cook until softened and slightly browned, 2-3 minutes per side.

In a large bowl, toss arugula with half the balsamic glaze. Season with salt and pepper to taste.

Remove flatbreads from oven and set broiler to high.

Carefully top flatbreads with blue cheese dressing, onion, Italian cheese blend, pear, walnuts, and as many chili flakes as you like.

Return to top rack and broil until cheese is melted, 2-3 minutes (for 4 servings, broil in batches).

Drizzle flatbreads with as much remaining balsamic glaze as you like. Top with salad and cut into pieces.

Divide between plates and serve.