Take the puff pastry out of the fridge and remove it from the packaging. Let it come to room temperature before unrolling it—this helps prevent tearing.
1 roll shop-bought puff pastry
Before starting, have all your ingredients ready—caramel burns quickly if left unattended.In a small saucepan over medium-low heat, pour in the sugar. The sugar will begin to melt: first becoming a little liquidy, then clumpy, and eventually turning into a deep amber-colored caramel.
150 g granulated sugar
Once the caramel turns amber, stir in the butter, cinnamon, and vanilla extract. Keep stirring until the butter is fully melted.
Quickly pour the caramel into a rectangular baking dish or casserole dish. Use a spatula to spread it evenly across the bottom. (You’ll need to work fast—caramel hardens quickly.)
Preheat your oven to 392°F (200°C).Trim the leaves off the rhubarb, rinse the stalks, and cut them into 4-inch (10 cm) pieces. Arrange the rhubarb over the caramel in the dish.
450 g rhubarb stalks
Unroll the puff pastry and place it over the rhubarb. Tuck any excess dough inwards along the edges of the dish to form a border.
Prick the top of the pastry a few times with a fork to allow steam to escape and ensure even baking.Bake for about 30 minutes, or until the pastry is golden brown.
Let the tart cool for about 5 minutes, then carefully invert the dish onto a serving plate to release the tart.
Enjoy warm or cold with a scoop of vanilla ice cream or freshly whipped cream.