Prepare the fish – Combine the ground cumin, smoked paprika, garlic powder and sea salt. Spread out on a plate. Press the fish fillets into the spice rub to generously coat each piece on both sides.
Start the fish – To a heavy skillet over medium-high heat, add a drizzle of oil or butter. Place fish portions in the hot pan. Cook 2 to 3 minutes.
Finish the fish – Gently lift the edge of the fillets to check for doneness. The fish should be white on at least the side against the heat. Turn carefully with a flat spatula. Cook another 2 to 3 minutes. Remove from the pan and set aside.
Sauté the tomatoes and aromatics – Add the tiny tomatoes to the skillet over medium-high heat. Cook until you see a good amount of brown blistering or even bursting. Add the onion, and garlic. Sauté and additional 2-3 minutes until onions soften.
De-glaze – Add the beer or broth to the skillet. Bring to a boil, and reduce by about half.
Finish the pan sauce – Add the jalapeño and citrus juice. Season with sea salt and fresh ground pepper. Simmer an additional 5 minutes.
Serve the Pan-Seared Mexican Fish – Add the cooked fish back into the skillet. Spoon sauce over the top. Garnish with chopped fresh cilantro and/or scallions as desired. Enjoy!