Pastel de Belém (Original Custard Tart)

Preheat oven to 230°C (450°F). Unroll puff pastry sheet on a lightly floured surface, brush with melted butter, then roll up tightly. Cut into 12 even slices. Place each slice cut-side down into greased muffin tin cups and press evenly to form a thin pastry cup extending above the rim.

In a saucepan, combine milk, sugar, cinnamon stick, and lemon zest. Heat over medium until just boiling, stirring occasionally. Remove from heat and let steep for 10 minutes.

In a bowl, whisk egg yolks with flour and vanilla extract. Slowly pour the warm milk mixture through a strainer into the yolk mixture, whisking constantly to avoid curdling.

Divide custard evenly among the 12 pastry cups (about 3 tbsp each).

Bake 15-20 minutes until pastry is golden and custard is set with dark spots. Cool in pan 5 minutes, then transfer to a wire rack. Dust warm tarts with powdered sugar and cinnamon.

Serve warm or at room temperature. Best the same day.