1. To make the pastry, sift the flour and salt into a large mixing bowl. Rub in the butter with your fingertips until it resembles fine bread crumbs. Beat 2 of the eggs with 2 tbsp water, add to the bowl, and stir until the dough holds together. Make a thick disk, cover with plastic wrap, and refrigerate for 30 minutes.

2. Meanwhile, heat the oil in a frying pan over medium heat. Cook the onion, stirring often, for about 5 minutes, or until translucent. Add the tomatoes and tomato paste, and simmer, stirring often, about 10 minutes, until thick. Remove from the heat and stir in the tuna and parsley. Season with salt and pepper.

3. Preheat the oven to 375°F (190°C). Roll out the dough to a thickness of 1/16 in (2mm). Cut out 24 rounds with a 3½ in (9cm) round cookie cutter. Fill each with a spoonful of the filling. Brush the edges with water, fold over, and press the edges closed with a fork.

4. Place the empanadas on an oiled baking sheet and brush with the remaining egg. Bake for about 15 minutes, or until golden. Serve warm.

Variation

Experiment with other fillings: replace the tuna with chopped cooked chicken or chorizo, or with diced cooked potato.