In a large bowl, combine the pre-cooked cornmeal and salt.
Gradually add the warm water, mixing with your hands until a smooth dough forms.
Let the dough rest for about 5 minutes to allow the cornmeal to absorb the water.
Knead in the vegetable oil until the dough is smooth and pliable.
In a large skillet, heat the vegetable oil over medium heat.
Add the finely chopped onion, minced garlic, and bell pepper. Sauté until the vegetables are softened, about 5 minutes.
Add the ground beef or shredded chicken and cook until browned and cooked through.
Stir in the chopped tomato, ground cumin, paprika, salt, and black pepper. Cook for another 5 minutes.
If using, add the chopped green olives and raisins. Mix well and cook for another 2 minutes. Remove from heat and let the filling cool slightly.
Divide the dough into 8 equal portions. Roll each portion into a ball.
On a piece of plastic wrap or parchment paper, flatten each dough ball into a circle about 1/4 inch (0.6 cm) thick.
Place a spoonful of the filling in the center of each dough circle.
Fold the dough over the filling to create a half-moon shape. Press the edges together to seal, then crimp with a fork.
In a large skillet or deep fryer, heat vegetable oil to 350°F (175°C).
Carefully add the empanadas to the hot oil, a few at a time, and fry until golden brown and crispy, about 3-4 minutes per side.
Use a slotted spoon to remove the empanadas from the oil and drain on paper towels.
Enjoy your meal!