Prepare the dough: Warm the water and wine until just lukewarm (about 95°F/35°C). Dissolve the yeast in this mixture and set aside. In the bowl of a stand mixer (or by hand), add 3 1/4 cups flour (reserve 1/4 cup), sugar, and salt. Mix briefly, then add the olive oil and continue mixing. Add one egg.

Add the yeast mixture and the paprika. Mix a bit, then knead for 15-20 minutes, until the dough is smooth and flexible. On a lightly floured surface, shape the dough into a ball. Place it in a bowl, cover with plastic wrap, and let it rise until doubled in size, about 1 1/2 hours.

For the filling: Slice the onions into thin strips, peel and finely chop the garlic, and dice the green bell pepper. Heat a generous amount of oil in a pot, add the chopped garlic and onions, season with salt to taste, and mix well.

Cook over medium-low heat for 35 minutes, stirring often. Add the green bell pepper and cook for another 40 minutes on low heat. Once the mixture is soft and cooked down, transfer it to a colander and drain well.

Preheat the oven to 350°F (180°C). Roast the red bell pepper for 40 minutes. Let it cool, then remove the skin and seeds, slice into strips, and set aside. Place the drained onion mixture in a large bowl, add the tomato sauce, and adjust salt if needed. Set aside. Drain the tuna and set aside.

Assemble the empanada: On a lightly floured surface, knead the dough for a minute, then divide it into two pieces. Roll out one piece to fit your baking sheet. Line the baking sheet with parchment paper and place the rolled-out dough on it. Spread the filling evenly over the dough, leaving about 3/4 inch (2 cm) border around the edges.

Spread the drained tuna evenly over the filling, then add the roasted red pepper strips on top. Roll out the second piece of dough for the top, place it over the filling, and trim any excess. Seal the edges by folding the bottom dough over the top all around. Use any dough scraps to make decorative leaves if you like and place them on top.

Use scissors to make small cuts in the dough and a hole in the center to let steam escape. Brush the top with beaten egg. Bake in a preheated oven at 375°F (190°C), with heat from top and bottom, on a rack in the lower-middle position, for 30 to 40 minutes, or until golden brown. Let cool before serving. Enjoy!