Mix water, vinegars, agave syrup, and salt together in the saucepan and bring to a very low simmer.
While the pickling liquid is coming up to temperature, thinly slice red onion. You want very thin strips, around ⅛-inch thin.
Pack red onion into a pickling jar and once the pickling liquid starts to simmer pour it over the onions in the pickling jar. Set aside and let cool / rest completely.
Get the Fish Started
Measure all of the spices into a sealable container. Put on the container lid and shake thoroughly to mix.
Lay the fish fillets out on the baking sheet and remove pin bones, if any. Dust fairly generously with the spice mix then place the sheet into the preheated oven for 20 minutes on the middle rack.
While the fish is cooking, make the creamy sauce and the cabbage slaw.
Once cooked, if desired, turn your broiler on high and broil for an additional two to three minutes for crispy edges then remove from the heat and let rest for five minutes.
Make the Creamy Sauce
Scoop mayonnaise sour cream into a mixing bowl. Crush the garlic clove and add it to the bowl.
Add lime juice and hot sauce and whisk cream together.
If the consistency is too thick you can thin it out by adding more lime juice or a little bit of water until it reaches your desired consistency. Transfer to the squeeze bottle for dressing, if desired.
Create the Cabbage Slaw
Thinly slice the green and purple cabbage and place into a large bowl. Julienne the carrot into 2-inch long strips sliced very thin and add to the cabbage.
Finely chop the cilantro and finely dice the jalapeño removing the pith and seeds to keep it mild, then add these to the bowl with the cabbage and carrots.
Toss together with the lime juice and then squeeze in about a tablespoon of the creamy dressing. Toss together to coat and season to taste.
Plating Up Your Dish
Preheat your skillet to medium high heat.
Lightly toast a couple of tortillas then while still warm, squeeze a thin line of creamy dressing down the middle of the tortilla.
Break up your cooked fish into chunks, and place a small pile of fish along the middle of the tortilla on top of the creamy dressing. Add a generous amount of prepared slaw, top with avocado slices and pickled onion.
Optionally squeeze a little bit more of the creamy dressing on top of the taco fillings.
Optionally crumble a bit of cotija cheese along the top of the taco fillings.