Method
In a large mixing bowl, combine the masa Harina and salt.
Gradually add the warm water and vegetable oil, stirring until the dough is smooth and well combined.
Cover the dough with a damp cloth and set aside to rest for 10 minutes.
In a large skillet, cook the ground pork over medium-high heat until browned and cooked through.
Add the onion, green bell pepper, and garlic to the skillet and cook until the vegetables are soft and translucent.
Add the cumin, oregano, salt, and black pepper to the skillet and stir well.
Pour in the tomato sauce and water, and stir to combine.
Reduce the heat to low and simmer the pork mixture for 10-15 minutes, or until the sauce has thickened.
Preheat a Comal or griddle over medium-high heat.
Take a small amount of the masa dough (about 1/4 cup) and form it into a ball.
Flatten the ball into a disc shape, about 1/2 inch thick.
Spoon a small amount of the pork filling (about 2 tbsp.) onto the center of the masa disc.
Fold the edges of the masa disc up and around the filling, pinching the edges together to seal.
Place the stuffed masa cake onto the preheated Comal or griddle and cook for 2-3 minutes on each side, or until golden brown and cooked through.
Serve hot with your choice of toppings.