In a medium saucepan, boil the tomatoes, jalapenos, oregano, and garlic salt for about 8 minutes, or until tomatoes have cooked down to a liquid. Remove from heat and let cool slightly. *Transfer to a blender and puree until smooth. Return sauce to pan, add chopped onion and cilantro, and stir well. Heat through and keep warm until ready to serve.

Heat oil in a large skillet over medium-high heat (you can use as little as 2 tablespoons oil to up to 1/2-inch deep). Season fish with salt and pepper and then carefully place in the pan; this may require adding the fish in 2 batches if your skillet is not large enough to hold all 4 fillets. Saute or pan-fry the fish until cooked on 1 side (fish will be opaque on that side). Carefully flip fish and continue cooking until cooked on second side and cooked through in the middle; the fish should be opaque in the middle. Cooking time will vary based on thickness of the fish fillets and the type of fish, but it should not take more than 3 to 5 minutes on each side. Transfer fish onto a serving platter or each of 4 dinner plates and top with the sauce. Serve immediately.

*When blending hot liquids: Remove liquid from the heat and allow to cool for at least 5 minutes. Transfer liquid to a blender or food processor and fill it no more than halfway. If using a blender, release one corner of the lid. This prevents the vacuum effect that creates heat explosions. Place a towel over the top of the machine, pulse a few times then process on high speed until smooth.