Empanada Gallega

Name: Empanada Gallega
Ingredients: FOR THE DOUGH; 2 medium onions (thinly sliced); 3 cloves garlic; ½ cup sunflower oil; ½ cup olive oil; 5 1/3 cups unbleached all-purpose flour; 2 tsp instant dry yeast; 1 ½ tsp salt; 1 tsp of sugar; 1 ½ cups warm water; FOR THE FILLING; 1 large green bell pepper; 1 large red bell pepper; Oil reserved from the dough; Reserved onion and garlic from the dough recipe; 3 cans high quality tuna; 2 cups homemade tomato sauce or 1 15oz can of tomato puree.; Salt to taste; Ground pepper; 1 egg (lightly beaten)