Preheat the oven to 400° F (205° C). Line a half-sheet rimmed baking tray with parchment.

In a small bowl, whisk together goat cheese, lemon juice, and lemon zest. Season with salt and pepper, to taste.

Unroll puff pastry and trim to approximately 9 x 12 inches. (If your pastry sheet is a square instead of a rectangle, use a rolling pin to roll it a few inches longer.) Arrange on prepared tray.

With a small stepped palette knife, spread the goat cheese mixture over the pastry, allowing a 1-inch border around the outer edge.

Arrange the asparagus in a straight line on top of the goat cheese.

With a pastry brush, apply a thin layer of beaten egg along the pastry border.

Turn up the edges, wrapping the pastry around the ends of the asparagus.

Crimp with a fork.

Brush the crimped edges with more of the beaten egg.

Sprinkle with grated Parmesan and chili flakes. Season with salt and pepper.

Bake in preheated oven for 25-30 minutes, or until pastry turns flaky and golden brown. Sprinkle with fresh thyme leaves. Serve warm.

Puff pastry tart is best served on the day it is made. Wrap leftovers in foil and store in the refrigerator for up to 2 days. Do not reheat.