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.

Place flatbreads, dimpled sides down, on a baking sheet. (For 4 servings, divide flatbreads between two baking sheets.)  Rub tops with a drizzle of olive oil; season with salt and pepper. TIP: Line the baking sheet with foil first for easy cleanup!

Toast on top rack until golden brown and crisp, 3-5 minutes. (For 4, toast on top and middle racks, swapping rack positions halfway through.)  

Meanwhile, heat a drizzle of oil in a large pan over medium-high heat. Add sausage* and onion. Cook, breaking up meat into pieces, until sausage is browned and cooked through and onion is softened, 4-6 minutes.

Once flatbreads are toasted, remove sheet from oven. Carefully flip flatbreads dimpled sides up; evenly spread with marinara and sprinkle with mozzarella. Top with sausage and onion.

Return flatbreads to top rack and bake until cheese melts and flatbread edges are golden brown, 5-6 minutes. (For 4 servings, bake on top and middle racks, swapping rack positions halfway through.)

Once flatbreads are done, drizzle with as much pesto and balsamic glaze as you like.

Slice flatbreads as desired. Divide between plates and serve.