In a medium saucepan, combine diced rhubarb, hulled and quartered strawberries, granulated sugar, cornstarch, and lemon zest. Stir gently to coat the fruit evenly.

Set the saucepan over medium heat and cook for about 5 minutes until the sugar dissolves and the mixture starts to bubble.

Continue cooking for an additional 8–10 minutes until it thickens and coats the back of a spoon. Remove from heat and cool.

Preheat your oven to 400°F (200°C). Roll out the refrigerated crusts on a floured surface, then cut into six equal squares.

Line a baking sheet with parchment paper.

Place about 2 tablespoons of the cooled fruit filling on one half of each pastry square. Fold the pastry over and press to seal.

Crimp edges with a fork and cut slits on top. Brush with egg wash and sprinkle coarse sugar.

Bake in the preheated oven for 20–25 minutes until puffed and golden.

Let the turnovers cool on a wire rack for a few minutes before serving.

Serve warm, optionally with vanilla ice cream.