Step 1

Adjust oven rack to middle position and heat oven to 475 degrees. Toss squash with ½ teaspoon salt in large bowl; transfer to colander and let drain in sink for 10 minutes. Line rimmed baking sheet with parchment paper. Place pie dough round in center of prepared sheet. Spread Boursin evenly over dough, leaving 1-inch border at edge. Sprinkle cheese with lemon zest.

Step 2

Spread squash over clean dish towel; cover with second towel and press firmly to remove as much liquid as possible. Transfer squash to now-empty bowl and toss with 1 tablespoon oil and ½ teaspoon pepper. Arrange squash in even overlapping layer over Boursin. Fold 1-inch edge of dough over filling, pleating every 2 to 3 inches and pinching to secure. Bake tart until crust is golden and squash is tender, about 15 minutes.

Step 3

Whisk lemon juice, honey, mustard, and remaining 1/2 teaspoon salt, 3 tablespoons oil, and 1/2 teaspoon pepper together in now-empty bowl. Add arugula and toss to combine. Cut tart into 4 equal pieces and serve with salad.