1. In a bowl, mix flour, 1 tablespoon sugar, and salt. Cut in cold butter until pea-sized pieces remain.

2. Stir in sourdough starter until dough forms. Add cold water if needed. Shape into a disk, wrap, and refrigerate 30 minutes.

3. Preheat oven to 400°F (200°C). Toss strawberries with 2 tablespoons sugar, cornstarch, vanilla, and lemon. Drain excess juice.

4. Roll chilled dough into a 12-inch circle on parchment. Transfer to baking tray. Pile strawberry mixture in center, leaving a 2-inch border.

5. Fold dough edges over filling, pleating as needed. Brush crust with beaten egg and sprinkle coarse sugar on top.

6. Bake 30–35 minutes until crust is golden and filling bubbles. Cool on a rack 15 minutes before slicing.

7. Serve warm or room temperature, optionally with ice cream or whipped cream.