Line a baking sheet with foil (line 2 baking sheets for 4 servings). Place prepared sheet on top rack (top and middle racks for 4) and preheat oven to 450 degrees. Wash and dry all produce. Trim and halve squash lengthwise, then cut crosswise into thin half-moons. Trim and thinly slice scallions. Halve lemon. Halve tomatoes lengthwise. Pick basil leaves from stems; discard stems and roughly chop leaves.

Heat a drizzle of olive oil in a large pan over medium-high heat. Add scallions and cook, stirring, until fragrant, 30 seconds to 1 minute.

Add squash to pan with scallions and cook, stirring, until softened and lightly browned, 4-5 minutes. Season with salt and pepper. Turn off heat.

Place flatbreads on prepared baking sheet. Tear mozzarella into small pieces and scatter over flatbreads. Top with squash mixture. Bake until cheese is melted and flatbreads are golden brown, 10-12 minutes. (For 4 servings, swap rack positions halfway through baking.)

Meanwhile, in a medium bowl, toss mixed greens, tomatoes, a squeeze of lemon juice, and a drizzle of olive oil. Season with salt and pepper.

Once flatbreads are done, scatter with chopped basil, pepitas, and chili flakes to taste. Drizzle with honey. Cut into slices and serve with salad on the side.