In a medium bowl, mix together the flour and baking powder. Place in the freezer for a minimum of 30 minutes to chill, or until you're ready to fry. Place the can/bottle of beer in the fridge to make sure it's super cold.
Once the banana blossoms are marinated, remove them from the marinade and place on a plate. Using a very sharp knife, slice them into taco-sized portions (around 2-3 inches long).
If necessary, heat your tortillas in a dry frying pan and wrap in a napkin to keep warm.
Place a medium, high-sided saucepan on a medium heat and add around 3-4 inches of vegetable oil. Using a probe or candy thermometer, bring the oil to 170c. Once the oil is to temperature, reduce to heat to low.
Remove the flour mixture form the freezer and pour in the beer. Mix well until you have a thick, smooth batter. Take two pieces of banana blossom and dunk them in the batter, making sure they're nicely coated. Carefully place them both in the hot oil (they should sizzle immediately). Fry for a total of around 2 minutes, flipping half-way through, or until golden brown all over. Remove from the oil and place on a plate lined with kitchen towel. Repeat the process with the remaining pieces of banana blossom. If any of the pieces go soggy or cold while waiting for the later pieces to fry, give them a second fry to crisp them back up.
To assemble, take a tortilla and add some slaw, followed by a piece of "fish", topped with some pickled onions, a good squirt of baja sauce, some diced avocado, coriander, a sprinkle of Tajin and a squeeze of lime juice.