Make pastry by combining in a bowl or food processor the flour, salt, sugar, and lemon zest. Cut in butter and olive oil with processor until mixture resembles very coarse meal. Rub ingredients between your fingertips if not using food processor. Add yolk and water, tossing until dough forms moist crumbles. Gather into a ball and let rest at room temperature while buttering a 16-inch pizza pan or a large cookie sheet. On a floured surface, roll out dough to an 18-inch circle and fit it into the pan, trimming away overhang. Chill 30 minutes to overnight.

Preheat oven to 400 degrees. Blend filling ingredients in a
large bowl and let stand at room temperature. After 30 minutes, bring pastry to room temperature. With a slotted spoon transfer filling to cover half the dough (reserve its liquid),leaving a 1-1/2 inch border at its rim. Top apples
with the sliced butter.

Moisten pastry edges with water. This dough is fragile -- guide it carefully with both hands to cover the filling, forming a half moon. If it tears, simply press torn edges together. Seal edges and crimp.

Brush crust with reserved filling liquid and cut 3 slashes into top. Bake 50 minutes to 1 hour, or until the tart is a rich brown color and crisp. Apples should be soft when pierced with a knife through one of the vent holes.

After resting 10 minutes, use 2 spatulas to gently slide the tart from the pan onto a large oval platter (or serve from the baking pan). Cool and cut across the tart's width into slices. Serve topped with a spoonful of whipped cream.