Step 1

Preheat oven to 400 degrees. On a floured surface, roll the puff pastry into a 16-by-10-inch rectangle. Trim uneven edges. Place pastry on a baking sheet. With a sharp knife, lightly score pastry dough 1 inch in from the edges to mark a rectangle. Using a fork, pierce dough inside the markings at 1/2-inch intervals. Bake until golden, about 15 minutes.

Step 2

Remove pastry shell from oven, and sprinkle with Gruyere. Trim the bottoms of the asparagus spears to fit crosswise inside the tart shell; arrange in a single layer over Gruyere, alternating ends and tips. Brush with oil, and season with salt and pepper. Bake until spears are tender, 20 to 25 minutes.