Apple and Onion Tart

In large bowl, combine flour, salt and mustard.

Using pastry blender or two knives, cut in butter until coarse crumbs form.

In liquid measure and using fork, beat yolk with vinegar until frothy; pour in enough ice water to make 1/3 cup (75 mL).

Drizzle over flour mixture, stirring briskly with fork until dough holds together.

Press into disc and wrap in plastic wrap; refrigerate for about 30 minutes or until firm. (Make ahead: Refrigerate for up to 3 days; let stand at room temperature for 15 minutes before rolling out.)

On lightly floured surface, roll out pastry to fit over bottom and all the way up sides of an 8-inch (2 L) springform pan.

Refrigerate for 30 minutes or until firm.

Line pastry with foil; fill evenly with pie weights or dried beans.

Bake in bottom third of 400°F (200°C) oven for 20 minutes.

Remove foil and weights; bake for 10 minutes or until light golden.

Let cool on rack.

Meanwhile, in skillet, melt butter over medium heat; cook onion for about 5 minutes or until softened.

Increase heat to medium high, add apples; cook for 2 minutes. Set aside.

In bowl, whisk together eggs, cream, parsley, chives, rosemary, Dijon mustard, salt and pepper.

Sprinkle half the cheese evenly over pie shell.

Spread apple mixture over top.

Gently pour egg mixture over top; sprinkle with remaining cheese.

Bake in bottom third of 375°F (190°C) oven for about 30 minutes or until golden and knife inserted in centre comes out clean.