To make the pastry, whisk together flour, sugar and salt in a large bowl. Add cold butter and toss to coat. Using your fingertips, rub butter into flour mixture until it resembles coarse crumbs. Whisk egg yolk with 1 tablespoon of water in a small bowl and drizzle into flour mixture while gently tossing with a fork. Continue to mix dough until dry ingredients are moistened and it holds together in clumps but does not yet form a ball. Drizzle in up to one more tablespoon of water if dough is too dry. Turn the crumbly dough out onto a clean work surface and gather it together in a ball with your hands slightly cupped, turning it frequently and pressing in loose bits until it is cohesive. Shape into a disk and wrap tightly with plastic wrap. Refrigerate at least 2 hours.

Let pastry sit at room temperature about 10 minutes before rolling to make it easier to work with. On a lightly floured work surface roll pastry out to just over 1/8-inch thickness. Cut out as many 5-inch rounds as you can and fit the rounds into 5-inch round tart pans (I got enough to make four 5-inch tarts and one small 3-inch tart). Trim away excess dough as necessary and refrigerate until pastry is firm, about 20 minutes.

To make the caramel topping, pour sugar in an even layer in a 1-quart saucepan. Add golden syrup and vinegar. Drizzle water around the edges of the sugar and bring the mixture to a boil over medium heat without stirring. Cook until caramel is a dark amber colour, swirling the pan periodically to colour evenly, 10-15 minutes. The sugar may look grainy before it turns into a clear syrup. Wash down the sides of pan with a pastry brush dipped in water to dissolve any crystals that may form. When caramel is almost ready, the large bubbles will subside and a golden brown foam will appear at the surface. Remove caramel from heat and very carefully stir in the cream until smooth. Be cautious as the caramel will bubble up violently once you add the cream. Stir in salt and cinnamon. Pour caramel into a heatproof measuring cup and let cool about 15 minutes.

Preheat your oven to 350°F.

To assemble the tarts, arrange apples in two layers over chilled pastry shell. Drizzle slightly cooled caramel evenly over apples. Sprinkle pecans over filling and place tarts on a baking tray to capture any juices that may leak out. Bake for 25-30 minutes on bottom third rack of the oven until caramel is bubbling. Transfer tarts to a wire rack to cool slightly before serving.