How to make
Chop the onion and peppers and saute them, until they soften. Pour in the tomato puree, or the same quantity of ripe, shredded tomatoes. Season with sugar, salt to taste, cover with a lid and simmer for 40 minutes.
Mix the cooked tomato sauce with the tuna, and the pine nuts, slightly roasted in a dry pan.
Prepare the dough by mixing the orange juice, water, olive oil, egg yolk and salt. Whisk well, sift in the flour and knead a soft, oily dough. If it feels too soft, you can add a little flour, so you can roll it out easier later.
Form 2 identical balls from the dough and roll out each ball. With the first one you can work directly on a sheet of baking paper, so it doesn't fall apart while transfering it, since the dough is a bit delicate.
Place the filling on top leaving, 0.4″ (1 cm) space at the edges. Place the other sheet of dough, on the filling and form it gently with your fingers if needed. Pinch the two sheets together, until they are firmly sealed. Don't worry if your dough has one or two cracks, as long as they are on top.
Brush your Empanada with egg wash made of 1 egg white and slide it into a preheated oven to 390°F (200 degrees). Decrease the temperature to 360°F (180 degrees) right after you put the Empanada in the oven. Bake for 45 minutes.
Let it cool for a while, and cut it into squares. You can serve it warm, or at room temperature.
Enjoy!
