Make the Fish. In a large skillet, warm olive oil over medium-high heat, then add the onions. Cook 3-4 minutes, stirring often. Add garlic and cook for about 1 minute, just until fragrant. Add tomatoes, jalapeno, and lime juice. Cook just until heated through, 1-2 minutes.
Season one side of the fish with a sprinkling of salt, pepper, and cumin. Add whole fish fillets to the skillet and cook for about 5 minutes, gently breaking up the fish into bite-sized chunks, until the fish is cooked through and the liquid in the skillet is slightly reduced. Be careful not to stir too aggressively or the fish will disintegrate. Sprinkle with cilantro and remove from the heat.
Make the Slaw. Toss cabbage together with additional cilantro, lime juice, and salt. Set aside to top tacos, as desired.
Assemble. Char or warm the tortillas briefly, then assemble tacos with fish, slaw, avocado, and more lime or cilantro, as desired. Enjoy!
Notes
Yield: For our family, this recipe yields about 8 medium tacos. Adjust the serving sizes accordingly depending on the size of your tortillas.
Heat: Dial the heat up or down simply by including more or less jalapeno. I usually make these fairly mild by removing all of the ribs and seeds, and sometimes include just 1/2 of a pepper. Adjust to your taste!