Preheat oven to 400°F (200°C). Line a baking sheet with parchment paper.
To prepare the fennel, trim off the stalks and fronds, keeping the fronds for later. Slice a thin piece from the root end, cut the bulb in half lengthwise, remove the tough core, then slice thinly for the recipe.
Heat olive oil in a skillet. Add onion and fennel. Season and cook 8 to 10 minutes until soft and browned. Stir in lemon juice.
Roll pastry to 10 x 15 inches. Score border and dock center. Brush edges with egg.
Bake 10 minutes until lightly golden.
Press down center. Spread fennel mixture inside border. Top with olives.
Bake for 5 more minutes or until heated through. Top with lemon zest and fennel fronds. Slice and serve.
Video
Notes
Keep pastry cold before baking. Do not overfill. Store leftovers in the fridge up to 3 days and reheat in the oven for the best texture.Store leftovers in the fridge for up to 3 days. Reheat in a 350°F oven until crisp again. I do not recommend the microwave because it results in soggy pastry.